Climate of the British Isles

Last updated December 28, 2023

The British Isles are an archipelago off the northwest coast of Europe, consisting of the islands of Great Britain and Ireland along with smaller surrounding ones. Its position allows dry continental air from Eurasia to meet wetter air from the Atlantic Ocean, which causes the weather to be highly variable, often changing many times during the day. It is defined as a temperate oceanic climate, or Cfb on the Köppen climate classification system. It is significantly warmer than other regions on the same latitude, previously thought to be due to the warmth provided by the Gulf Stream; however, this has been disproven, and most of the mild temperatures have been linked to the Rocky Mountains and the heat storing capabilities of the North Atlantic Ocean.^[1] Temperatures do not often switch between great extremes, with warm summers and mild winters.

Temperature

The British Isles undergo very small temperature variations. This is due to its proximity to the Atlantic, which acts as a temperature buffer, warming the Isles in winter and cooling them in summer. Coastal areas tend to be more temperate than inland areas, as the influence of the ocean is less acute. Valleys can be especially cold, as cool air collects in them during the winter. July is usually the warmest month, with the highest temperatures being found closest to Continental Europe, in south-east England.

Sunshine and cloud

The sunniest times are the months of May and June, whereas December has the least sunshine. The clearest skies in the British Isles occur over the south of England, due to the winds from the continent. Equally, mountainous areas, especially in the North-west receive barely any sunshine, sometimes less than 1000 hours a year. In winter on north-south valleys there are sometimes only a few hours of sunshine in a day.

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. Fog is more common inland and on higher altitudes; mainly during winter and during the morning at times of high pressure.

On occasions blocking anticyclones (high pressure systems) may move over the British Isles, 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.

Precipitation

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Rainfall varies across the Isles, with a general trend to more rain as you go west and in higher elevations. December and January are usually the wettest months. The mountain ranges are the wettest areas in the U.K.^[2] These are some of the wettest locations in Britain.^[3]^[4] Most rainfall comes from North Atlantic depressions occur throughout the year and are particularly frequent and intense in the autumn and winter. They can on occasions bring prolonged periods of heavy rain, and flooding is quite common.

Snow can occur during winter months, most frequently occurring during January and February. Hail is relatively common, and is most common during the summer months. Each of the United Kingdom's 50 strongest hailstorms on record since 1650 have occurred between the months of May and September.^[5]

Winds

The prevailing winds over the British Isles are from the west^[6] and south-west,^[7] and winds are strongest to the north and west.^[8] Generally, the coast tends to be windier than inland areas; and the west tends to be windier than the east.^[6]

Gales – which are defined as winds with speeds above 34 knots (39 mph; 63 km/h) for any ten consecutive minutes – are strongly associated with the passage of deep depressions across the area. The Hebrides typically experience a 25 days a year containing gales.^[9]

Severe weather

The British Isles do not experience extreme weather regularly. There have been several occasions where extreme weather events have occurred. In the winter of 1982, for a few days parts of central and southern England experienced temperatures lower than central Europe and Moscow. In contrast, the summers of 1975 and 1976 experienced temperatures as high as 35 °C (95 °F). It was so dry the country suffered drought and water shortages.^[10] Extended periods of extreme weather, such as the drought of 1975–1976 and 2022 as well as the very cold winters of 1946–1947, 1962–1963, 1978–79, 1981–1982 and 2009–2010, are often caused by blocking anticyclones which can persist several days or even weeks. In winter they can bring long periods of cold dry weather and in summer long periods of hot dry weather.

Cyclones

Tropical cyclones themselves do not affect the British Isles due to the cold temperature of the surrounding ocean. Any tropical cyclone that comes near the Isles has said to have undergone a process called extratropical transition. The Isles do experience these extratropical cyclones, the Great Storm of 1987 was a deep depression which formed in the Bay of Biscay, which also contained the remnants of Hurricane Floyd.^[11] Hurricane Lili of 1996 and Hurricane Gordon of 2006 both were strong extratropical cyclones with tropical storm-force winds, which caused transport closures, power-cuts and flooding. In 2011, the remnants of Hurricane Katia brought near hurricane-force winds to Scotland, with sustained winds reaching 70 mph (110 km/h) while centred over the Isle of Lewis. In 2017, Hurricane Ophelia brought severe storms to Ireland, and carried Saharan dust and smoke from wildfires in Portugal into the atmosphere over the United Kingdom, creating red and orange skies across the country.

Thunderstorms

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Thunderstorms are most common in London, the South-East, east of England, the East Midlands, and least common in the North-West. Greater London, Kent, Sussex, Essex, Hertfordshire, Cambridgeshire, Suffolk and Norfolk are the regions with the most thunderstorms during the year. The South-West and the West Midlands also get storms but usually less severe. ^[12] Occasionally, thunderstorms can be severe and produce large hailstones as seen in Ottery St Mary, Devon in October 2008, where drifts reached 1.8 metres (5 ft 11 in).^[13]

Climate change

Estimates produced by the Met Office predict average annual temperature to increase by 2 °C (4 °F) and the warmest summer day to increase by 3 °C (6 °F) by the 2050s. Average winter rainfall is also likely to increase and most areas will see a slight decrease in annual rainfall.^[14]

Recent events

In the early 21st century, the British Isles have undergone some record breaking events. In 2004-2006, a partial drought caused fires to break out throughout the south of Great Britain, and water restrictions were introduced in some areas. The drought problems were solved due to the unusually wet period between October 2006 and July 2007, which had higher than average rainfall.

The year 2006 was an unusually warm one. Although the year started off cool, from April the weather stayed warmer than average. July was the hottest month on record for the United Kingdom.^[15](The summer of 2022 has since reached 40C in some areas.)

Related Research Articles

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In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather, while high-pressure areas are associated with lighter winds and clear skies. Winds circle anti-clockwise around lows in the northern hemisphere, and clockwise in the southern hemisphere, due to opposing Coriolis forces. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere (aloft). The formation process of a low-pressure area is known as cyclogenesis. In meteorology, atmospheric divergence aloft occurs in two kinds of places:

The climate of India consists of a wide range of weather conditions across a vast geographic scale and varied topography. Based on the Köppen system, India hosts six major climatic sub types, ranging from arid deserts in the west, alpine tundra and glaciers in the north, and humid tropical regions supporting rain forests in the southwest and the island territories. Many regions have starkly different microclimates, making it one of the most climatically diverse countries in the world. The country's meteorological department follows the international standard of four seasons with some local adjustments: winter, summer, monsoon or rainy season, and a post-monsoon period.

The climate of Scotland is mostly temperate and oceanic, and tends to be very changeable, but rarely extreme. It is warmed by the Gulf Stream from the Atlantic, and given its northerly latitude it is much warmer than areas on similar latitudes, for example Kamchatka in Russia or Labrador in Canada, or Fort McMurray, Canada. Scots sometimes describe weather which is grey and gloomy using the Scots language word dreich.

The climate of Puerto Rico in the Köppen climate classification is predominantly tropical rainforest. Temperatures throughout the year are warm to hot, averaging near 85 °F (29 °C) in lower elevations and 70 °F (21 °C) in the mountains. Easterly trade winds pass across the island year round while the rainy season stretches from April into November. The relatively cool trade winds are blocked by the mountains of the Cordillera Central which causes rain shadows and sharp variations in the temperature and wind speed over short distances. About a quarter of the average annual rainfall for Puerto Rico occurs during tropical cyclones, which are more frequent during La Niña years.

Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to severe gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, about the center of the cyclone.

The climate of San Diego, California is classified as a hot-summer Mediterranean climate. The basic climate features hot, sunny, and dry summers, and cooler, wetter winters. However, San Diego is much more arid than typical Mediterranean climates, and winters are still dry compared with most other zones with this type of climate. The climate at San Diego International Airport, the location for official weather reports for San Diego, as well as the climate at most beach areas, straddles the border between BSh and BSk due to the mild winters and cool summers in these locations.

The characteristics of United States rainfall climatology differ significantly across the United States and those under United States sovereignty. Summer and early fall bring brief, but frequent thundershowers and tropical cyclones which create a wet summer and drier winter in the eastern Gulf and lower East Coast. During the winter, and spring, Pacific storm systems bring Hawaii and the western United States most of their precipitation. Low pressure systems moving up the East Coast and through the Great Lakes, bring cold season precipitation to from the Midwest to New England, as well as Great Salt Lake. The snow to liquid ratio across the contiguous United States averages 13:1, meaning 13 inches (330 mm) of snow melts down to 1 inch (25 mm) of water.

The climate of the north and central parts of the US state of Florida is humid subtropical. South Florida has a tropical climate. There is a defined rainy season from May through October when air mass thundershowers that build in the heat of the day drop heavy but brief summer rainfall.

Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms.

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The climate of the United States varies due to changes in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.

North Carolina's climate varies from the Atlantic coast in the east to the Appalachian Mountain range in the west. The mountains often act as a "shield", blocking low temperatures and storms from the Midwest from entering the Piedmont of North Carolina.

South Carolina has a humid subtropical climate, with hot summers throughout most of the state. But, an exception does occur in the Blue Ridge Mountains, as outlier pockets of an Oceanic Climate do exist. Mild winters predominate in the eastern and southern part of the state, but cool to occasionally cold winters are the standard in the northwestern area of the state, especially areas at or above 600 feet in elevation. On average, between 40 and 80 inches of precipitation falls annually across the state, potentially even in excess of 100 inches in portions of the Appalachian temperate rainforest. Tropical cyclones, and afternoon thunderstorms due to hot and humid conditions, contribute to precipitation during the summer and sometimes fall months, while extratropical cyclones contribute to precipitation during the fall, winter, and spring months. The coast experiences nearly all of their tropical weather impacts from storms coming directly from the Atlantic coast. The northwestern area of the state can receive impacts from both Atlantic basin storms moving westward from the coast and also occasionally very heavy rainfall and flooding from storms originating from the Gulf of Mexico that move inland towards the northeast after making landfall from the Florida Panhandle to Louisiana.

The climate of Ireland is mild, humid and changeable with abundant rainfall and a lack of temperature extremes. Ireland's climate is defined as a temperate oceanic climate, or Cfb on the Köppen climate classification system, a classification it shares with most of northwest Europe. The island receives generally warm summers and cool winters.

Vietnam has a monsoon-influenced climate typical of that of mainland Southeast Asia. The diverse topography, long latitude, and influences from the South China Sea lead to climatic conditions varying significantly between regions. The northern region experiences a monsoonal and temperate climate (Cfa) with four distinct seasons with winters typically dry and summers ranging from hot to mild. In more southern areas, the climate is tropical monsoon (Aw) with only two seasons. In addition, a temperate climate exists in mountainous areas, which are found in Sa Pa and Da Lat, while a more continental climate exists in Lai Châu Province and Sơn La Province.

The climate of Wales refers to the weather conditions prevailing in Wales in general or over a long period.

The climate of south-west England is classed as oceanic (Cfb) according to the Köppen climate classification. The oceanic climate is typified by frequent cloudy skies, cool winters with cool summers and precipitation all year round, with more experienced in winter. Annual rainfall is about 1,000 millimetres (39 in) and up to 2,000 millimetres (79 in) on higher ground. Exceptions include areas to the east of high ground ( e.g. Exeter / parts of West Somerset that are subject to a rain shadow effect and annual rainfall is closer to 30 inches.

Droughts are a relatively common feature of the weather in the United Kingdom, with one around every 5–10 years on average. These droughts are usually during the summer, when a blocking high causes hot, dry weather for an extended period. However this means that droughts can vary in their characteristics. All types of drought cause issues across all sectors, with impacts extending to the ecosystem, agriculture and the economy of the whole country in severe cases of drought. The south east of the country usually suffers most, as it has the highest population and the lowest average precipitation per year, which is even lower in a drought. Even in these areas in severe droughts, the definition, impacts, effects and management are all minimal in comparison to drought prone areas such as Australia and parts of the United States. In recent years however, the summers of 2007, 2008, 2009, August 2010 and 2012 were wetter than normal, 2007 being wettest on record. Droughts have continued to occur in recent times, with spring 2011, July 2013, summer 2018, spring 2020, spring and summer 2022 and May and June 2023 all featuring excessively dry periods for part or all of the UK, and will likely become more severe due to climate change over the 21st century.

Cyprus has a subtropical climate - Mediterranean and semi-arid type - according to Köppen climate classification signes Csa and BSh, with very mild winters and warm to hot summers. Snow is possible only in the Troodos mountains in the central part of the island. Rain occurs mainly in winter, with summer being generally dry.

References

↑ "Forget about the Gulf Stream: Britain is really kept warm in winter by". 10 February 2003.
↑ "Rainfall Amount (mm) Annual Average". Met Office. Archived from the original on 2013-07-19. Retrieved 2008-04-13.
↑ Clark, Ross (2006-10-28). "The wetter, the better". The Independent . Archived from the original on 2012-01-28. Retrieved 2009-09-02.
↑ Philip, Catherine (2005-07-28). "40 die as one year's rain falls in a day". The Times . London. Retrieved 2009-09-02.
↑ "Weather Facts: Hailstorms in Britain | weatheronline.co.uk".
1 2 "Climate of the British Isles" (PDF). Met Office. National Meteorological Library and Archive. Retrieved 4 November 2023.
↑ "Factors effecting the unique climate of the UK". BBC Bitesize. BBC. Retrieved 4 November 2023.
↑ "Where are the windiest parts of the UK?". Met Office. Met Office. Retrieved 4 November 2023.
↑ "Western Scotland: climate" (PDF). Met Office. Met Office. Retrieved 4 November 2023.
↑ "The 1976 Drought averages". British Broadcasting Corporation. Archived from the original on April 12, 2006. Retrieved 2006-08-01.
↑ "Hurricanes". The BBC. Archived from the original on February 14, 2009. Retrieved 2009-04-14.
↑ "Days of Thunder Annual Average". Met Office. Retrieved 2007-08-14.
↑ "Hailstorm sparks 'absolute chaos'". BBC News. 2008-10-30. Retrieved 2009-10-30.
↑ "UKCP Map". The Met Office . Retrieved 9 December 2009.
↑ McKie, Robin (October 15, 2006). "Official: this summer is the longest, hottest ever". The Observer . Retrieved 2006-11-05.

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[1] "Forget about the Gulf Stream: Britain is really kept warm in winter by". 10 February 2003.

[4577mm-2] "Rainfall Amount (mm) Annual Average". Met Office. Archived from the original on 2013-07-19. Retrieved 2008-04-13.

[3] Clark, Ross (2006-10-28). "The wetter, the better". The Independent . Archived from the original on 2012-01-28. Retrieved 2009-09-02.

[4] Philip, Catherine (2005-07-28). "40 die as one year's rain falls in a day". The Times . London. Retrieved 2009-09-02.

[5] "Weather Facts: Hailstorms in Britain | weatheronline.co.uk".

[metoffice-british-isles-6] 1 2 "Climate of the British Isles" (PDF). Met Office. National Meteorological Library and Archive. Retrieved 4 November 2023.

[7] "Factors effecting the unique climate of the UK". BBC Bitesize. BBC. Retrieved 4 November 2023.

[8] "Where are the windiest parts of the UK?". Met Office. Met Office. Retrieved 4 November 2023.

[metoffice-western-scotland-9] "Western Scotland: climate" (PDF). Met Office. Met Office. Retrieved 4 November 2023.

[1976drought-10] "The 1976 Drought averages". British Broadcasting Corporation. Archived from the original on April 12, 2006. Retrieved 2006-08-01.

[11] "Hurricanes". The BBC. Archived from the original on February 14, 2009. Retrieved 2009-04-14.

[thunder-12] "Days of Thunder Annual Average". Met Office. Retrieved 2007-08-14.

[13] "Hailstorm sparks 'absolute chaos'". BBC News. 2008-10-30. Retrieved 2009-10-30.

[14] "UKCP Map". The Met Office . Retrieved 9 December 2009.

[2006July-15] McKie, Robin (October 15, 2006). "Official: this summer is the longest, hottest ever". The Observer . Retrieved 2006-11-05.

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