CLIMATE OF THE UNITED KINGDOM
The United Kingdom straddles the geographic higher mid-latitudes between 49 and 61 N. It is on the western seaboard of Afro-Eurasia, the world's largest land mass. These conditions allow convergence between moist maritime air and dry continental air. In this area, the large temperature variation creates atmospheric instability and this is a major factor that influences the often unsettled weather the country experiences, where many types of weather can be experienced in a single day. In general the climate of the UK is cool and often cloudy, and hot temperatures are infrequent.
The climate in the United Kingdom is defined as a temperate oceanic climate, or Cfb on the Köppen climate classification system, a classification it shares with most of northwest Europe.[1] Regional climates are influenced by the Atlantic Ocean and latitude. Northern Ireland, Wales and western parts of England and Scotland, being closest to the Atlantic Ocean, are generally the mildest, wettest and windiest regions of the UK, and temperature ranges here are seldom extreme. Eastern areas are drier, cooler, less windy and also experience the greatest daily and seasonal temperature variations. Northern areas are generally cooler, wetter and have slightly larger temperature ranges than southern areas.
Though the UK is mostly under the influence of the maritime tropical air mass from the south-west, different regions are more susceptible than others when different air masses affect the country: Northern Ireland and the west of Scotland are the most exposed to the maritime polar air mass which brings cool moist air; the east of Scotland and north-east England are more exposed to the continental polar air mass which brings cold dry air; the south and south-east of England are more exposed to the continental tropical air mass which brings warm dry air (and consequently most of the time the warmest summer temperatures); and Wales and the south-west of England are the most exposed to the maritime tropical air mass which brings warm moist air.
If the air masses are strong enough in their respective areas during the summer, there can sometimes be a large difference in temperature between the far north of Scotland (including the Islands) and south-east of England – often a difference of 10–15 °C (18-27 °F) but sometimes of as much as 20 °C (36 °F) or more. An example of this could be that in the height of summer the Northern Isles could have temperatures around 15 °C (59 °F) and areas around London could reach 30 °C (86 °F).
SEASONS
SPRING
Spring is the period from March to May. Spring is generally a calm, cool and dry season, particularly because the Atlantic has lost much of its heat throughout the autumn and winter. However, as the sun rises higher in the sky and the days get longer, temperatures can rise relatively high, but often tend to drop off again at night due to the cool oceans and the warm weather dependent solely on the sun. Thunderstorms and heavy showers can develop occasionally particularly towards the end of the season.
There is a fair chance of snow earlier in the season when temperatures are colder - indeed, snow falling in the first half of March is quite common. Often, there is no significant drop in either snowfall or freezing temperatures between February & March, when the surrounding Atlantic is at its coldest. Some of the country's heaviest snowfalls of recent years have happened in the first half of March and snow showers can occur infrequently until mid-April. They have been known to develop as late as mid-May over some areas of the country, such as in 2013 when snow was recorded on 14 May over parts of Staffordshire, Herefordshire and Wales. Snow was also recorded at lower levels in early June 1975.
Early spring can be quite cold, and occasionally the lowest temperatures of the year can occur in March, as it did at Heathrow Airport on 5 March 2001, 4 March 2006 & 8 March 2011. Temperatures below freezing are not unusual in March, even in the south of the UK. On the other hand, high temperatures above 30 °C are generally rare but can occur on occasion, the most recent instance occurring on 25 May 2012. It was even hotter on 27 May 2005, where 31.9 °C was recorded in London. Rarely, the hottest day of the year can be in spring. As stated below May 27 was the hottest day of the year in 2012 in most parts of the UK.
Mean temperatures in Spring are markedly influenced by latitude. Most of Scotland and the mountains of Wales and northern England are the coolest areas of the UK, with average temperatures ranging from −0.6 to 5.8 °C . The southern half of England experiences the warmest spring temperatures of between 8.8 and 10.3 °C.
SUMMER
Summer lasts from June to August and is the warmest and usually the sunniest season. Rainfall totals can have a wide local variation due to localised thunderstorms. These thunderstorms mainly occur in southern, eastern, and central England and are less frequent and severe in the north and west.[18] North Atlantic depressions are not as severe in summer but increase both in severity and frequency towards the end of the season. Summer can see high pressure systems from the Azores High.
Climatic differences at this time of year are more influenced by latitude and temperatures are highest in southern and central areas and lowest in the north. Summer temperatures rarely exceed 35 °C (95 °F), but when this does occur it happens more frequently in London and the South East than other parts of the country. Scotland and northern England have the coolest summers (average means: 12.2 to 14.8 °C (54.0 to 58.6 °F)), while Wales and the south-west of England have warmer summers (average means: 14.9 to 15.4 °C (58.8 to 59.7 °F)) and the south and south-east of England have the warmest summers (average means: 15.5 to 17.7 °C (59.9 to 63.9 °F)).[19] The record maximum is 38.5 °C (101.3 °F) recorded in Faversham, Kent on 10 August 2003.
It is worth noting that a disputed temperature of 39.0 °C (102.2 °F) was recorded at an airfield near Wisley, Surrey on 18 July 2006, during a prolonged heatwave which surprised many meteorologists for not breaking the temperature record set in August 2003, despite being the hottest month ever recorded. Similarly, a disputed temperature of 38.0 °C (100.4 °F) was recorded in Luton on 1 August 1995, which whilst would now have been exceeded, would have held the record until August 2003. It is speculated that higher temperatures may have been recorded in the hot summers of 1908, 1911, 1948, 1955, 1975, 1976, 1983, 1990, 1995 and 2006 (and indeed 2003 itself), which would at least break their own highest temperatures, if not this official figure.
In recent years, some very high temperatures have been recorded only briefly - when warm air is dragged over the country from the south for a day or two. Many meteorologists nickname this a 'flashbang' heatwave, and it is not unusual for it to set off or be followed by intense thundery downpours, or to drag weather fronts with it. It is in these conditions that the highest temperatures in both 2014 - on 17 & 18 July - and 2015 - on 30 June & 1 July - have been recorded. High temperatures can return after thundery conditions or weather fronts pass, as it did between 22 & 24 July 2014. Patterns like this have also occurred further in the past - for example, on 18 & 19 June 2000 and on 28 & 29 July 2002, which is quite notable for severe thunderstorms.
Summers in the 21st century have been a mixed bag, with some long, hot summers (2003, 2006 & 2013), and others which will be remembered solely for flooding caused by downpours (2002, 2004, 2007, 2008, 2012 and 2015). The summer of 2012 was so appalling that March is humorously considered to have been the height of summer, being the only drier than average month throughout the year in many places. For some places in 2012, 27 May was the hottest day of the year.[20] This follows on from an indifferent summer in 2011, in which in Aberdaron, 21 April was the hottest day of the year.[21] Summer 2015 was particularly mixed, with a flash-bang heatwave in the south-east breaking the July temperature with 36.7 °C (98.1 °F) recorded on 1 July, whilst the rest of the country experienced a poor summer, with August in particular being very wet. Despite the mixed summers the UK experiences, somewhere in the UK on at least one occasion has recorded 30 °C or above since 1993. At Heathrow Airport, the last summer in which temperatures did not reach 30 °C was 2007.
AUTUMN
Autumn in the United Kingdom lasts from September to November.[22] The season is notorious for being unsettled—as cool polar air moves southwards following the sun, it meets the warm air of the tropics and produces an area of great disturbance along which the country lies. This combined with the warm ocean due to heating throughout the spring and summer, produces the unsettled weather of autumn. In addition, when the air is particularly cold temperatures on land may be colder than the ocean, resulting in significant amounts of condensation and clouds which bring rain to the country.
Atlantic depressions during this time can become intense and winds of hurricane force (greater than 119 km/h or 74 mph) can be recorded. Western areas, being closest to the Atlantic, experience these severe conditions to a significantly greater extent than eastern areas. As such, autumn, particularly the latter part, is often the stormiest time of the year. One particularly intense depression was the Great Storm of 1987. A very severe storm affected the UK on 27 October 2002, and the autumn of 2013 was also littered with severe storms, including the St. Jude's Storm on 28 October 2013.
Autumn can also be a cold season at times - in recent years, very low temperatures and heavy snowfall have been recorded during November 1985, November 1993 & November 2010, which set a new record low of -18.0 °C in Wales on 28 November 2010. Snow also fell rather widely across the UK on 28 & 29 October 2008, causing traffic problems where it settled on the M4. Even further south, low temperatures can be recorded, with temperatures well below freezing as far south as Heathrow Airport between 29 & 31 October 1997 - for context, the low of 30 October 1997 recorded was lower than any recorded at this station in March, November or December 1997 and even the following January, 1998 - only the low temperatures on 2 & 4 February 1998 prevented it from being the lowest temperature of the winter at this station. The first frosts of the winter are usually recorded between October & December, but they are quite unusual in September except on high ground when the surrounding ocean is at or near its warmest. It is not particularly unusual for September to be warmer than June, as it was in 1999.[23]
However, the United Kingdom sometimes experiences an 'Indian Summer', where temperatures particularly by night can be very mild and rarely fall below 10 °C (50 °F). Such events are aided by the surrounding Atlantic Ocean and seas being at their warmest, keeping the country in warm air, despite the relatively weak sun. Examples of this were in 1985, 1999, 2005, 2006, 2011[24] and 2016 where September and October even more so, saw above average temperatures which felt more like a continuation of summer than autumn. Autumns since 2000 have been very mild with notable extremes of precipitation; the UK has seen some of its wettest and driest autumns since the millennium. In fact, 2011 and 2016 were notable as many areas of the country recorded their highest temperatures of the year in September and October (for example, 28.2 °C at Hawarden on 1 October, 26.3 °C at St. Athan on 2 October 2011 and the UK's highest temperature of 2016 on 13 September with 34.4 °C at Gravesend).[25]
Coastal areas in the southern half of England have on average the warmest autumns, with mean temperatures of 10.7 to 13.0 °C (51.3 to 55.4 °F).[26] Mountainous areas of Wales and northern England, and almost all of Scotland, experience mean temperatures between 1.7 and 7.5 °C (35.1 and 45.5 °F).[26]
WINTER
Winter in the UK is defined as lasting from December to February. The season is generally cool, wet and windy. Temperatures at night rarely drop below −10 °C (14 °F) and in the day rarely rise above 15 °C (59 °F). Precipitation is plentiful throughout the season, though snow is relatively infrequent despite the country's high latitude: The only areas with significant snowfall are the Scottish highlands and the Pennines, where at higher elevations a colder climate determines the vegetation, mainly temperate coniferous forest, although deforestation has severely decreased forest area. For a majority of the landmass snow is possible but not frequent, apart from the higher altitudes, where snow can lie 1–5 months or even beyond 6 months.
Towards the later part of the season the weather usually stabilises with less wind, less precipitation and lower temperatures. This change is particularly pronounced near the coasts mainly because the Atlantic ocean is often at its coldest during this time after being cooled throughout the autumn and the winter. The early part of winter however is often unsettled and stormy; often the wettest and windiest time of the year.
Snow cover on The Saddle in the Scottish Highlands
Snow falls intermittently and mainly affects northern and eastern areas, high ground in Wales and especially the mountains of Scotland where the amount of lying snow is frequently high enough to permit skiing at one of the five Scottish ski resorts. These resorts usually operate between December and April depending on the snowfall each winter. Frequently in the mountains potent depressions may move in from the north in the form of 'polar lows', introducing heavy snow and often blizzard-like conditions to parts of the United Kingdom, particularly Scotland. During periods of light winds and high pressure frost and fog can become a problem and can pose a major hazard for drivers on the roads.
Mean winter temperatures in the UK are most influenced by proximity to the sea. The coldest areas are the mountains of Wales and northern England, and inland areas of Scotland, averaging −3.6 to 2.3 °C (25.5 to 36.1 °F).[27] Coastal areas, particularly those in the south and west, experience the mildest winters, on average 5 to 8.7 °C (41.0 to 47.7 °F).[27] Hardiness zones in the UK are high, ranging from zone 7 in the Scottish Highlands, the Pennines and Snowdonia, to zone 10 on the Isles of Scilly. Most of the UK lies in zones 8 or 9.[28] In zone 7, the average lowest temperature each year is between −17.7 and −12.3 °C (0.1 and 9.9 °F), and in zone 10, this figure is between −1.1 and 4.4 °C (30.0 and 39.9 °F).[29]
Snow in the UK falls almost every year but in small quantities. The UK can suffer extreme winters like 1684, 1740, 1795 (when London received its record lowest temperature of −21.1 °C (−6.0 °F)), 1947 and 1963. In 1963 it snowed on Boxing Day in the UK and snow lasted in most areas until 6 March with blizzards through February, which had significant and documented effects on the FA Cup - Wrexham were forced to play on sand for one tie. In modern times snow has generally become rarer but the UK can still get heavy falls, such as in 1978/79, 1981/82, 1986/87 and 1990/91. The winter of 2008/09 produced the heaviest snowfall since 1991, and the winter of 2009-10 was even more severe, with many parts of the United Kingdom experiencing the coldest and snowiest winters since 1978/79; temperatures plummeted to −22.3 °C (−8.1 °F) at Altnaharra, Sutherland – close to the −22.9 °C (−9.2 °F) recorded at the southernmost part of the globe at the same period. The record for the lowest temperature ever recorded in the UK still remains −27.2 °C (−17.0 °F) which was recorded on 10 January 1982 and 11 February 1895 in Braemar, Scotland and on 30 December 1995 in Altnaharra, Scotland. December 2010 was the coldest December in 120 years; the CET (Central England Temperature) was -0.7 °C, meaning it was the coldest month since February 1986, and the coldest December since 1890. Many places experienced heavy snowfall and extreme cold, temperatures regularly fell below −10.0 °C (14.0 °F)) across many areas. However, the cold subsided after Christmas Day, 2010. It is worth also noting that November 2010 saw an extremely severe cold snap, with lows of −18.0 °C (−0.4 °F)) in Llysdinam on 28 November. The month saw temperatures below average, despite what was actually a very mild first half. Spring 2013 was also notoriously cold - March 2013 was the coldest month of the winter (and indeed 2013 as a whole), which is quite striking given that December 2012, January and February 2013 were all also below average in terms of temperature. The following winter was the opposite - in many places, only on 11 & 12 January was any snow recorded, and the entire country was battered by a series of severe depressions and storms. The St. Jude's day storm first affected the UK on 26 October 2013, and many places saw no respite until a high swept across the country on 2 March 2014. Parts of the Somerset levels remained underwater for most of the winter and well into spring. Record-equalling gusts of 142 mph were recorded off the north coast of Scotland on 5 December 2013, with notably severe storms also recorded on 2 November 2013, 24 December 2013, 3 January 2014 & 14 February 2014.
In the 1990s and 2000s, most of the winters were milder and usually wetter than average with daytime temperatures going below freezing a rare occurrence. In fact, the winter of 1995/1996 was the only one which was defined as below average in terms of the UK as a whole, although February 1991 saw heavy snowfall & January 1997 was cold in the South. The winters of 2008/09, 2009/10 and 2010/11 have however seen a different pattern with these three winters being defined as below or well below average with large snowfall amounts widespread and very low temperatures; this was the first time three consecutive cold winters in the UK have occurred since the 1960s. Since the winter of 2012/2013, winters have been mild (exceptionally so in 2013/2014 and 2015/2016), although exceptionally wet. The winter of 2014/2015 was an oddity, in that it was generally quiet and sunny.
December 2015 became the wettest calendar month ever recorded in the United Kingdom, with January 2016 becoming the second wettest. In these months, some northern and western parts had 2 to 4 times as much rainfall as normal.[30] December 2015 was also the warmest December averaged over the whole UK, and had the highest positive anomaly for any month in the Central England temperature series which began in 1659 (CET was 9.7 °C, this is warmer than even any March[31]). Most areas of southern England had average monthly temperatures 5-6 °C above normal. Some plants flowered that would normally do so in the Spring or even Summer.[32] Hardly any stations in Wales and Southern England recorded any air frosts and temperatures were often comparable to those of April or May. The maximum recorded temperature was 17.2 °C at Teignmouth in Devon and Plockton and Achnagart in the highlands of Scotland on 16th. The lowest daily mean temperature during December 2015 at Heathrow Airport was still 8.2 °C on 9 December, comparable to the average daily high for the calendar month. Remarkably, December 2015 did not break any national records for high temperatures, just failing to reach the maximum England temperature of 17.7 °C recorded on 2 December 1985 in Chivenor, Devon and on 11 December 1994 in Penkridge, Staffordshire.[33] Despite the warmth, it was the dullest December since 1989.[34]
SUNSHINE AND CLOUD
A sunny spring day
The average total annual sunshine in the United Kingdom is 1339.7 hours, which is just under 30% of the maximum possible.[35] (The maximum hours of sunshine possible in one year is approximately 4476 hours.) The south coast of England often has the clearest skies because cumulus cloud formation generally takes place over land, and prevailing winds from the south-west keep this cloud from forming overhead. The counties of Dorset, Hampshire, Sussex and Kent are the sunniest areas, which have annual average totals of around 1,750 hours of sunshine per year,[36] and many South coastal areas of England receive more than 2000 hours of sunshine on regular years. On the other hand, Northern, western and mountainous areas are generally the cloudiest areas of the UK, with some mountainous areas receiving fewer than 1,000 hours of sunshine a year.[36]
An overcast day in Plymouth, south-west England
Valley areas such as the South Wales Valleys, due to their north-south orientation, receive less sunshine than lowland areas because the mountains on either side of the valley obscure the sun in the early morning and late evening. This is noticeable in winter where there are only a few hours of sunshine. The mountains of Wales, northern England and Scotland can be especially cloudy with extensive mist and fog. Near the coast, sea fog may develop in the spring and early summer. Radiation fog may develop over inland areas of Great Britain and can persist for hours or even days in the winter and can pose a major hazard for drivers and aircraft.
On occasions blocking anticyclones (high pressure systems) may move over the United Kingdom, which can persist for weeks or even months. The subsided, dry air often results in clear skies and few clouds, bringing frosty nights in winter and hot days in the summer, when some coastal areas can achieve almost maximum possible sunshine for periods of weeks.
Average hours of sunshine in winter range from 38–108 hours in some mountainous areas and western Scotland, up to 217 hours in the south and east of England;[37] while average hours of sunshine in summer range from 294–420 hours in northern Scotland and Northern Ireland, to 600–760 hours in southern English coastal counties.[38] The most sunshine recorded in one month was 383.9 hours at Eastbourne (East Sussex) in July 1911.[36]
The Atlantic Ocean
One of the greatest influences on the climate of the UK is the Atlantic Ocean and especially the North Atlantic Current, which brings warm waters from the Gulf of Mexico to the waters around the country by means of thermohaline circulation. This has a powerful moderating and warming effect on the country's climate—the North Atlantic Drift warms the climate to such a great extent that if the current did not exist then temperatures in winter would be about 10 °C (18 °F) lower than they are today. The current allows England to have vineyards at the same latitude that Canada has polar bears. A good example of the effects of the North Atlantic Drift is Tresco Abbey Gardens, on the Isles of Scilly, 48 kilometres (30 mi) west of Cornwall, where Canary Island date palm trees grow - possibly the nearest of their kind to the Arctic Circle, at 50° latitude north. These warm ocean currents also bring substantial amounts of humidity which contributes to the notoriously wet climate that western parts of the UK experience.
The extent of the Gulf Stream's contribution to the actual temperature differential between North America and western Europe is a matter of dispute.[39][40] It has been argued that atmospheric waves that bring subtropical air northwards contribute to a much greater extent to the temperature differential than thermohaline circulation.[39]
Winds
Further information: List of atmospheric pressure records in Europe
The high latitude and proximity to a large ocean to the west means that the United Kingdom experiences strong winds. The prevailing wind is from the south-west, but it may blow from any direction for sustained periods of time. Winds are strongest near westerly facing coasts and exposed headlands.
The United Kingdom straddles the geographic higher mid-latitudes between 49 and 61 N. It is on the western seaboard of Afro-Eurasia, the world's largest land mass. These conditions allow convergence between moist maritime air and dry continental air. In this area, the large temperature variation creates atmospheric instability and this is a major factor that influences the often unsettled weather the country experiences, where many types of weather can be experienced in a single day. In general the climate of the UK is cool and often cloudy, and hot temperatures are infrequent.
The climate in the United Kingdom is defined as a temperate oceanic climate, or Cfb on the Köppen climate classification system, a classification it shares with most of northwest Europe.[1] Regional climates are influenced by the Atlantic Ocean and latitude. Northern Ireland, Wales and western parts of England and Scotland, being closest to the Atlantic Ocean, are generally the mildest, wettest and windiest regions of the UK, and temperature ranges here are seldom extreme. Eastern areas are drier, cooler, less windy and also experience the greatest daily and seasonal temperature variations. Northern areas are generally cooler, wetter and have slightly larger temperature ranges than southern areas.
Though the UK is mostly under the influence of the maritime tropical air mass from the south-west, different regions are more susceptible than others when different air masses affect the country: Northern Ireland and the west of Scotland are the most exposed to the maritime polar air mass which brings cool moist air; the east of Scotland and north-east England are more exposed to the continental polar air mass which brings cold dry air; the south and south-east of England are more exposed to the continental tropical air mass which brings warm dry air (and consequently most of the time the warmest summer temperatures); and Wales and the south-west of England are the most exposed to the maritime tropical air mass which brings warm moist air.
If the air masses are strong enough in their respective areas during the summer, there can sometimes be a large difference in temperature between the far north of Scotland (including the Islands) and south-east of England – often a difference of 10–15 °C (18-27 °F) but sometimes of as much as 20 °C (36 °F) or more. An example of this could be that in the height of summer the Northern Isles could have temperatures around 15 °C (59 °F) and areas around London could reach 30 °C (86 °F).
SEASONS
SPRING
Spring is the period from March to May. Spring is generally a calm, cool and dry season, particularly because the Atlantic has lost much of its heat throughout the autumn and winter. However, as the sun rises higher in the sky and the days get longer, temperatures can rise relatively high, but often tend to drop off again at night due to the cool oceans and the warm weather dependent solely on the sun. Thunderstorms and heavy showers can develop occasionally particularly towards the end of the season.
There is a fair chance of snow earlier in the season when temperatures are colder - indeed, snow falling in the first half of March is quite common. Often, there is no significant drop in either snowfall or freezing temperatures between February & March, when the surrounding Atlantic is at its coldest. Some of the country's heaviest snowfalls of recent years have happened in the first half of March and snow showers can occur infrequently until mid-April. They have been known to develop as late as mid-May over some areas of the country, such as in 2013 when snow was recorded on 14 May over parts of Staffordshire, Herefordshire and Wales. Snow was also recorded at lower levels in early June 1975.
Early spring can be quite cold, and occasionally the lowest temperatures of the year can occur in March, as it did at Heathrow Airport on 5 March 2001, 4 March 2006 & 8 March 2011. Temperatures below freezing are not unusual in March, even in the south of the UK. On the other hand, high temperatures above 30 °C are generally rare but can occur on occasion, the most recent instance occurring on 25 May 2012. It was even hotter on 27 May 2005, where 31.9 °C was recorded in London. Rarely, the hottest day of the year can be in spring. As stated below May 27 was the hottest day of the year in 2012 in most parts of the UK.
Mean temperatures in Spring are markedly influenced by latitude. Most of Scotland and the mountains of Wales and northern England are the coolest areas of the UK, with average temperatures ranging from −0.6 to 5.8 °C . The southern half of England experiences the warmest spring temperatures of between 8.8 and 10.3 °C.
SUMMER
Summer lasts from June to August and is the warmest and usually the sunniest season. Rainfall totals can have a wide local variation due to localised thunderstorms. These thunderstorms mainly occur in southern, eastern, and central England and are less frequent and severe in the north and west.[18] North Atlantic depressions are not as severe in summer but increase both in severity and frequency towards the end of the season. Summer can see high pressure systems from the Azores High.
Climatic differences at this time of year are more influenced by latitude and temperatures are highest in southern and central areas and lowest in the north. Summer temperatures rarely exceed 35 °C (95 °F), but when this does occur it happens more frequently in London and the South East than other parts of the country. Scotland and northern England have the coolest summers (average means: 12.2 to 14.8 °C (54.0 to 58.6 °F)), while Wales and the south-west of England have warmer summers (average means: 14.9 to 15.4 °C (58.8 to 59.7 °F)) and the south and south-east of England have the warmest summers (average means: 15.5 to 17.7 °C (59.9 to 63.9 °F)).[19] The record maximum is 38.5 °C (101.3 °F) recorded in Faversham, Kent on 10 August 2003.
It is worth noting that a disputed temperature of 39.0 °C (102.2 °F) was recorded at an airfield near Wisley, Surrey on 18 July 2006, during a prolonged heatwave which surprised many meteorologists for not breaking the temperature record set in August 2003, despite being the hottest month ever recorded. Similarly, a disputed temperature of 38.0 °C (100.4 °F) was recorded in Luton on 1 August 1995, which whilst would now have been exceeded, would have held the record until August 2003. It is speculated that higher temperatures may have been recorded in the hot summers of 1908, 1911, 1948, 1955, 1975, 1976, 1983, 1990, 1995 and 2006 (and indeed 2003 itself), which would at least break their own highest temperatures, if not this official figure.
In recent years, some very high temperatures have been recorded only briefly - when warm air is dragged over the country from the south for a day or two. Many meteorologists nickname this a 'flashbang' heatwave, and it is not unusual for it to set off or be followed by intense thundery downpours, or to drag weather fronts with it. It is in these conditions that the highest temperatures in both 2014 - on 17 & 18 July - and 2015 - on 30 June & 1 July - have been recorded. High temperatures can return after thundery conditions or weather fronts pass, as it did between 22 & 24 July 2014. Patterns like this have also occurred further in the past - for example, on 18 & 19 June 2000 and on 28 & 29 July 2002, which is quite notable for severe thunderstorms.
Summers in the 21st century have been a mixed bag, with some long, hot summers (2003, 2006 & 2013), and others which will be remembered solely for flooding caused by downpours (2002, 2004, 2007, 2008, 2012 and 2015). The summer of 2012 was so appalling that March is humorously considered to have been the height of summer, being the only drier than average month throughout the year in many places. For some places in 2012, 27 May was the hottest day of the year.[20] This follows on from an indifferent summer in 2011, in which in Aberdaron, 21 April was the hottest day of the year.[21] Summer 2015 was particularly mixed, with a flash-bang heatwave in the south-east breaking the July temperature with 36.7 °C (98.1 °F) recorded on 1 July, whilst the rest of the country experienced a poor summer, with August in particular being very wet. Despite the mixed summers the UK experiences, somewhere in the UK on at least one occasion has recorded 30 °C or above since 1993. At Heathrow Airport, the last summer in which temperatures did not reach 30 °C was 2007.
AUTUMN
Autumn in the United Kingdom lasts from September to November.[22] The season is notorious for being unsettled—as cool polar air moves southwards following the sun, it meets the warm air of the tropics and produces an area of great disturbance along which the country lies. This combined with the warm ocean due to heating throughout the spring and summer, produces the unsettled weather of autumn. In addition, when the air is particularly cold temperatures on land may be colder than the ocean, resulting in significant amounts of condensation and clouds which bring rain to the country.
Atlantic depressions during this time can become intense and winds of hurricane force (greater than 119 km/h or 74 mph) can be recorded. Western areas, being closest to the Atlantic, experience these severe conditions to a significantly greater extent than eastern areas. As such, autumn, particularly the latter part, is often the stormiest time of the year. One particularly intense depression was the Great Storm of 1987. A very severe storm affected the UK on 27 October 2002, and the autumn of 2013 was also littered with severe storms, including the St. Jude's Storm on 28 October 2013.
Autumn can also be a cold season at times - in recent years, very low temperatures and heavy snowfall have been recorded during November 1985, November 1993 & November 2010, which set a new record low of -18.0 °C in Wales on 28 November 2010. Snow also fell rather widely across the UK on 28 & 29 October 2008, causing traffic problems where it settled on the M4. Even further south, low temperatures can be recorded, with temperatures well below freezing as far south as Heathrow Airport between 29 & 31 October 1997 - for context, the low of 30 October 1997 recorded was lower than any recorded at this station in March, November or December 1997 and even the following January, 1998 - only the low temperatures on 2 & 4 February 1998 prevented it from being the lowest temperature of the winter at this station. The first frosts of the winter are usually recorded between October & December, but they are quite unusual in September except on high ground when the surrounding ocean is at or near its warmest. It is not particularly unusual for September to be warmer than June, as it was in 1999.[23]
However, the United Kingdom sometimes experiences an 'Indian Summer', where temperatures particularly by night can be very mild and rarely fall below 10 °C (50 °F). Such events are aided by the surrounding Atlantic Ocean and seas being at their warmest, keeping the country in warm air, despite the relatively weak sun. Examples of this were in 1985, 1999, 2005, 2006, 2011[24] and 2016 where September and October even more so, saw above average temperatures which felt more like a continuation of summer than autumn. Autumns since 2000 have been very mild with notable extremes of precipitation; the UK has seen some of its wettest and driest autumns since the millennium. In fact, 2011 and 2016 were notable as many areas of the country recorded their highest temperatures of the year in September and October (for example, 28.2 °C at Hawarden on 1 October, 26.3 °C at St. Athan on 2 October 2011 and the UK's highest temperature of 2016 on 13 September with 34.4 °C at Gravesend).[25]
Coastal areas in the southern half of England have on average the warmest autumns, with mean temperatures of 10.7 to 13.0 °C (51.3 to 55.4 °F).[26] Mountainous areas of Wales and northern England, and almost all of Scotland, experience mean temperatures between 1.7 and 7.5 °C (35.1 and 45.5 °F).[26]
WINTER
Winter in the UK is defined as lasting from December to February. The season is generally cool, wet and windy. Temperatures at night rarely drop below −10 °C (14 °F) and in the day rarely rise above 15 °C (59 °F). Precipitation is plentiful throughout the season, though snow is relatively infrequent despite the country's high latitude: The only areas with significant snowfall are the Scottish highlands and the Pennines, where at higher elevations a colder climate determines the vegetation, mainly temperate coniferous forest, although deforestation has severely decreased forest area. For a majority of the landmass snow is possible but not frequent, apart from the higher altitudes, where snow can lie 1–5 months or even beyond 6 months.
Towards the later part of the season the weather usually stabilises with less wind, less precipitation and lower temperatures. This change is particularly pronounced near the coasts mainly because the Atlantic ocean is often at its coldest during this time after being cooled throughout the autumn and the winter. The early part of winter however is often unsettled and stormy; often the wettest and windiest time of the year.
Snow cover on The Saddle in the Scottish Highlands
Snow falls intermittently and mainly affects northern and eastern areas, high ground in Wales and especially the mountains of Scotland where the amount of lying snow is frequently high enough to permit skiing at one of the five Scottish ski resorts. These resorts usually operate between December and April depending on the snowfall each winter. Frequently in the mountains potent depressions may move in from the north in the form of 'polar lows', introducing heavy snow and often blizzard-like conditions to parts of the United Kingdom, particularly Scotland. During periods of light winds and high pressure frost and fog can become a problem and can pose a major hazard for drivers on the roads.
Mean winter temperatures in the UK are most influenced by proximity to the sea. The coldest areas are the mountains of Wales and northern England, and inland areas of Scotland, averaging −3.6 to 2.3 °C (25.5 to 36.1 °F).[27] Coastal areas, particularly those in the south and west, experience the mildest winters, on average 5 to 8.7 °C (41.0 to 47.7 °F).[27] Hardiness zones in the UK are high, ranging from zone 7 in the Scottish Highlands, the Pennines and Snowdonia, to zone 10 on the Isles of Scilly. Most of the UK lies in zones 8 or 9.[28] In zone 7, the average lowest temperature each year is between −17.7 and −12.3 °C (0.1 and 9.9 °F), and in zone 10, this figure is between −1.1 and 4.4 °C (30.0 and 39.9 °F).[29]
Snow in the UK falls almost every year but in small quantities. The UK can suffer extreme winters like 1684, 1740, 1795 (when London received its record lowest temperature of −21.1 °C (−6.0 °F)), 1947 and 1963. In 1963 it snowed on Boxing Day in the UK and snow lasted in most areas until 6 March with blizzards through February, which had significant and documented effects on the FA Cup - Wrexham were forced to play on sand for one tie. In modern times snow has generally become rarer but the UK can still get heavy falls, such as in 1978/79, 1981/82, 1986/87 and 1990/91. The winter of 2008/09 produced the heaviest snowfall since 1991, and the winter of 2009-10 was even more severe, with many parts of the United Kingdom experiencing the coldest and snowiest winters since 1978/79; temperatures plummeted to −22.3 °C (−8.1 °F) at Altnaharra, Sutherland – close to the −22.9 °C (−9.2 °F) recorded at the southernmost part of the globe at the same period. The record for the lowest temperature ever recorded in the UK still remains −27.2 °C (−17.0 °F) which was recorded on 10 January 1982 and 11 February 1895 in Braemar, Scotland and on 30 December 1995 in Altnaharra, Scotland. December 2010 was the coldest December in 120 years; the CET (Central England Temperature) was -0.7 °C, meaning it was the coldest month since February 1986, and the coldest December since 1890. Many places experienced heavy snowfall and extreme cold, temperatures regularly fell below −10.0 °C (14.0 °F)) across many areas. However, the cold subsided after Christmas Day, 2010. It is worth also noting that November 2010 saw an extremely severe cold snap, with lows of −18.0 °C (−0.4 °F)) in Llysdinam on 28 November. The month saw temperatures below average, despite what was actually a very mild first half. Spring 2013 was also notoriously cold - March 2013 was the coldest month of the winter (and indeed 2013 as a whole), which is quite striking given that December 2012, January and February 2013 were all also below average in terms of temperature. The following winter was the opposite - in many places, only on 11 & 12 January was any snow recorded, and the entire country was battered by a series of severe depressions and storms. The St. Jude's day storm first affected the UK on 26 October 2013, and many places saw no respite until a high swept across the country on 2 March 2014. Parts of the Somerset levels remained underwater for most of the winter and well into spring. Record-equalling gusts of 142 mph were recorded off the north coast of Scotland on 5 December 2013, with notably severe storms also recorded on 2 November 2013, 24 December 2013, 3 January 2014 & 14 February 2014.
In the 1990s and 2000s, most of the winters were milder and usually wetter than average with daytime temperatures going below freezing a rare occurrence. In fact, the winter of 1995/1996 was the only one which was defined as below average in terms of the UK as a whole, although February 1991 saw heavy snowfall & January 1997 was cold in the South. The winters of 2008/09, 2009/10 and 2010/11 have however seen a different pattern with these three winters being defined as below or well below average with large snowfall amounts widespread and very low temperatures; this was the first time three consecutive cold winters in the UK have occurred since the 1960s. Since the winter of 2012/2013, winters have been mild (exceptionally so in 2013/2014 and 2015/2016), although exceptionally wet. The winter of 2014/2015 was an oddity, in that it was generally quiet and sunny.
December 2015 became the wettest calendar month ever recorded in the United Kingdom, with January 2016 becoming the second wettest. In these months, some northern and western parts had 2 to 4 times as much rainfall as normal.[30] December 2015 was also the warmest December averaged over the whole UK, and had the highest positive anomaly for any month in the Central England temperature series which began in 1659 (CET was 9.7 °C, this is warmer than even any March[31]). Most areas of southern England had average monthly temperatures 5-6 °C above normal. Some plants flowered that would normally do so in the Spring or even Summer.[32] Hardly any stations in Wales and Southern England recorded any air frosts and temperatures were often comparable to those of April or May. The maximum recorded temperature was 17.2 °C at Teignmouth in Devon and Plockton and Achnagart in the highlands of Scotland on 16th. The lowest daily mean temperature during December 2015 at Heathrow Airport was still 8.2 °C on 9 December, comparable to the average daily high for the calendar month. Remarkably, December 2015 did not break any national records for high temperatures, just failing to reach the maximum England temperature of 17.7 °C recorded on 2 December 1985 in Chivenor, Devon and on 11 December 1994 in Penkridge, Staffordshire.[33] Despite the warmth, it was the dullest December since 1989.[34]
SUNSHINE AND CLOUD
A sunny spring day
The average total annual sunshine in the United Kingdom is 1339.7 hours, which is just under 30% of the maximum possible.[35] (The maximum hours of sunshine possible in one year is approximately 4476 hours.) The south coast of England often has the clearest skies because cumulus cloud formation generally takes place over land, and prevailing winds from the south-west keep this cloud from forming overhead. The counties of Dorset, Hampshire, Sussex and Kent are the sunniest areas, which have annual average totals of around 1,750 hours of sunshine per year,[36] and many South coastal areas of England receive more than 2000 hours of sunshine on regular years. On the other hand, Northern, western and mountainous areas are generally the cloudiest areas of the UK, with some mountainous areas receiving fewer than 1,000 hours of sunshine a year.[36]
An overcast day in Plymouth, south-west England
Valley areas such as the South Wales Valleys, due to their north-south orientation, receive less sunshine than lowland areas because the mountains on either side of the valley obscure the sun in the early morning and late evening. This is noticeable in winter where there are only a few hours of sunshine. The mountains of Wales, northern England and Scotland can be especially cloudy with extensive mist and fog. Near the coast, sea fog may develop in the spring and early summer. Radiation fog may develop over inland areas of Great Britain and can persist for hours or even days in the winter and can pose a major hazard for drivers and aircraft.
On occasions blocking anticyclones (high pressure systems) may move over the United Kingdom, which can persist for weeks or even months. The subsided, dry air often results in clear skies and few clouds, bringing frosty nights in winter and hot days in the summer, when some coastal areas can achieve almost maximum possible sunshine for periods of weeks.
Average hours of sunshine in winter range from 38–108 hours in some mountainous areas and western Scotland, up to 217 hours in the south and east of England;[37] while average hours of sunshine in summer range from 294–420 hours in northern Scotland and Northern Ireland, to 600–760 hours in southern English coastal counties.[38] The most sunshine recorded in one month was 383.9 hours at Eastbourne (East Sussex) in July 1911.[36]
The Atlantic Ocean
One of the greatest influences on the climate of the UK is the Atlantic Ocean and especially the North Atlantic Current, which brings warm waters from the Gulf of Mexico to the waters around the country by means of thermohaline circulation. This has a powerful moderating and warming effect on the country's climate—the North Atlantic Drift warms the climate to such a great extent that if the current did not exist then temperatures in winter would be about 10 °C (18 °F) lower than they are today. The current allows England to have vineyards at the same latitude that Canada has polar bears. A good example of the effects of the North Atlantic Drift is Tresco Abbey Gardens, on the Isles of Scilly, 48 kilometres (30 mi) west of Cornwall, where Canary Island date palm trees grow - possibly the nearest of their kind to the Arctic Circle, at 50° latitude north. These warm ocean currents also bring substantial amounts of humidity which contributes to the notoriously wet climate that western parts of the UK experience.
The extent of the Gulf Stream's contribution to the actual temperature differential between North America and western Europe is a matter of dispute.[39][40] It has been argued that atmospheric waves that bring subtropical air northwards contribute to a much greater extent to the temperature differential than thermohaline circulation.[39]
Winds
Further information: List of atmospheric pressure records in Europe
The high latitude and proximity to a large ocean to the west means that the United Kingdom experiences strong winds. The prevailing wind is from the south-west, but it may blow from any direction for sustained periods of time. Winds are strongest near westerly facing coasts and exposed headlands.
