UK climate
The climate of the United Kingdom is a temperate , with warm summers, cool winters and abundant rainfall throughout the year. The most important influencing factors are the northern geographical latitude (between 50 ° and 61 ° N), the immediate vicinity of the Atlantic Ocean and, in particular, the warming of the water around the British Isles by the Gulf Stream . The UK is on the borderline of the convergence of warm tropical air in the south and cold polar air in the north. The weather can be extremely changeable and change from day to day, but the temperature differences are relatively small all year round.
The seasons
winter
The winter is generally a cool, wet and windy season. During the night the temperature hardly drops below −10 ° C, during the day it rarely rises above 15 ° C. Abundant rainfall occurs, occasionally in the form of snow . The first half of winter, often the wettest and windiest time of the year, is characterized by changeable and stormy weather. The weather usually stabilizes in the second half; precipitation is decreasing, winds are blowing less and temperatures are dropping. This change is particularly pronounced in the coastal areas because the Atlantic is coldest at this time of year.
Snowfall occurs mainly in the northern and eastern areas, mainly at higher elevations such as the Scottish mountains, where the snowpack is thick enough for several weeks to allow winter sports . In most areas, however, the snow barely stays in place for more than a week. The cold north and east winds, favored by high pressure areas , are usually replaced after a short time by warmer westerly winds, usually caused by low pressure areas in the North Atlantic ( Atlantic lows ). The low pressure systems often result in stormy winds and heavy rain showers, combined with mild temperatures. Very rarely, a polar low can be strong enough to cause blizzards to occur in some parts of the country (especially Scotland) . When the wind is weak and the air pressure is high, frost and fog form .
spring
The spring is generally a windless, cool and dry season. The main reason for this is that the Atlantic lost much of its warmth during autumn and winter. With the higher position of the sun and the longer time of day, temperatures rise and thunderstorms and heavy rains can occur. At low temperatures there is a possibility that snow will fall.
summer
In summer , temperatures are highest in the southern and central regions and tend to decrease towards the north. However, these hardly ever rise above 35 ° C. The record value is 38.5 ° C. In the north-west and north the temperatures are on average 14 to 15 ° C, in the south-west 16 ° C, in the south-east 17 to 18 ° C.
In general, summer is a relatively dry season, although thunderstorms can occur in the southern, eastern and central parts of the country. These are far less frequent and significantly less severe in the north and west. The Azores high is the most common high pressure weather situation, continental high pressure areas have hardly any influence on the weather. North Atlantic depressions are rare in summer, but increase in frequency and intensity towards the end of the season.
autumn
The British autumn is known to be extremely changeable. Cool polar air flows south and meets the warm air of the tropics. The seawater warmed up during spring and summer also contributes to the unstable weather conditions. When the air is colder than the ocean, increased condensation occurs, which allows rain clouds to form. The Atlantic low pressure systems are increasingly prevalent and cause violent winds that can even develop into hurricanes with top speeds of over 120 km / h. Especially the western areas are affected by these extreme winds.
It is not uncommon for the weather to be stable enough for an " Indian summer ". Especially during the night the temperatures are relatively mild and rarely fall below 10 ° C. The frequency of this phenomenon increases with global warming. Especially in October the temperatures are above their long-term average. The amount of precipitation has fluctuated considerably since the beginning of the 21st century; in the new millennium, the autumns were both the wettest and the driest.
Regional differences
The varying degrees of influence of the Atlantic Ocean result in the formation of regional climatic differences. The west of the United Kingdom has a milder, more humid and windier maritime climate due to its close proximity to the ocean ; the temperature fluctuations are also seldom extreme. In contrast, the eastern regions are more strongly influenced by the European continental climate , and the cooler water of the North Sea also has an influence. The climate is drier, cooler and less windy, the temperature differences are more pronounced. The islands in particular Orkney , Shetlands and the Channel Islands do not fit into the mainland scheme.
England
In general, the west and north of England are cooler and rainier than the rest of the area. The average amount of rain is around 1000 mm per year and is higher in higher elevations than in the plains. The wettest area is the Lake District in Cumbria with over 2000mm of rainfall annually. Essex is the driest county; the average annual rainfall is only 600 mm here, although rain falls here on over 100 days a year. In particularly dry years, the amount of precipitation even drops to just 450 mm per year, which is below the average for Beirut or Jerusalem . The highest temperature ever recorded in England is 38.5 ° C on August 10, 2003 near Faversham in Kent . The lowest temperature ever recorded is −26.1 ° C on January 10, 1982 near Newport in Shropshire . Since the average temperature is usually above freezing, even in winter, there is little snow.
Wales
The climate in Wales is comparable to that in England. Here, too, it is more humid in the north and west. The record high temperature is 35.2 ° C, measured on August 2, 1990 at Hawarden Bridge , Flintshire . The lowest temperature ever recorded was −23.3 ° C on January 21, 1940 in Rhayader , Radnorshire . As in England, the amount of snow in Wales is small in the lower elevations, but increases with altitude.
Scotland
The climate of Scotland is oceanic and leads to very changeable weather. In general, the west coast is warmer than the east coast. The reasons are on the one hand the influence of the warm Gulf Stream in the Atlantic Ocean, on the other hand the colder surface temperature of the North Sea. The amount of precipitation varies greatly depending on the region. In the western highlands there is an average of more than 3000 mm of precipitation per year; In comparison, the lowlands often have less than 800 mm of precipitation annually. In contrast to the Lowlands, heavy snowfalls are not uncommon in the Highlands, so winter sports are also possible there. The lowest temperature, −27.2 ° C, was recorded on December 30, 1995 at Altnaharra in Sutherland . The highest temperature ever recorded was 32.9 ° C on August 9, 2003 near St Boswells in the Scottish Borders region .
Northern Ireland
Northern Ireland has a balanced maritime climate. The prevailing wind usually blows from southwest to northeast. Frequent rains are characteristic of the entire region, with rainfall tending to be greater in the west than in the east. About 60% of the annual rainfall falls between August and January. The record high temperature of 30.8 ° C was measured on July 12, 1983 in Belfast , the lowest temperature ever recorded was −17.5 ° C on January 1, 1979 at Banbridge in County Down .
Sunshine and clouds
The average annual sunshine in the United Kingdom is relatively low, with around two thirds of all days partially or completely cloudy. On the south coast, however, the duration of sunshine is generally longer; the formation of cumulus cloud formations usually takes place over land, so that the coastal areas tend to be rather cloudless. In the southern counties of Dorset , Hampshire , Sussex and Kent , the average amount of sunshine a year is between 1750 and 2100 hours. Northwestern and mountainous regions, on the other hand, are far more often under a cloud cover, with less than 1000 hours of sunshine per year.
Cloud formation is particularly strong in mountainous regions, and there is also increased fog . The coastal areas are also heavily affected by fog, especially on winter nights. In many cases, the fog does not dissipate for days during the cold season. Occasionally, high pressure areas over the UK remain stable for weeks or even months. The dry air leads to a clear sky with few clouds and frosty nights in winter or hot days in summer.
The average daily sunshine duration in winter ranges from less than an hour in the low mountain ranges to five hours on the south coast. In summer these values are 4 to 8 hours and 6 to 10 hours respectively. The monthly maximum was reached in Eastbourne in July 1911 , when the sun shone for 383.9 hours.
Winch
The relatively high temperatures compared to the latitudes and the close proximity to a large ocean mean that the UK is very windy. The main wind direction is northwest, but with such a changeable climate, the wind can blow from all possible directions for a long time. The winds are particularly strong on the west coasts and also in flatter areas inland, where there are no mountains that have a slowing effect.
Strong winds (i.e. winds with a speed of approx. 60 to 100 km / h) occur particularly frequently when a particularly strong low pressure area passes, mainly in winter. The windiest place is the Hebrides , where strong winds occur on 35 days a year. Higher-lying areas are more often affected by strong winds than low-lying areas. On the Great Dun Fell in the Pennines (877 m above sea level), an average of 114 days of strong winds per year were recorded between 1963 and 1974. The highest speed ever recorded in the lowlands was 191 km / h on December 15, 1979 at Gwennap Head, Cornwall.
Rainfall
The amount of rain varies widely across the country. In general, the following applies: the further west and the higher it is, the greater the amount of precipitation . The Lake District is one of the wettest areas, with over 2000mm of rain per year. The mountains of Scotland and Wales, the Pennines and the moors of south west England are also particularly humid.
In contrast, the south, southeast and southern Midlands have less than 700 mm of rain per year. In London, for example, it rains less than in Rome , Sydney or New York . The driest region of the British Isles is Essex , with an average rainfall of around 600mm per year (although it rains for 90 days). In certain years the amount even falls below 450 mm - less than, for example, in Jerusalem or Beirut .
Most of the rain is caused by the North Atlantic lows that stretch across the UK and are particularly frequent and intense in the fall and winter. They occasionally cause prolonged periods of rain in the north, which leads to flooding . In recent years, however, pronounced dry periods have been observed, especially in the south, which has led to an increased lack of drinking water.
Temperatures
The annual average temperature in England ranges from 8.5 ° C in the north to 12 ° C in the south, although it can be a few degrees cooler in the higher elevations. This slight variation in temperature is due to the balancing influence of the Atlantic Ocean. Water can store more heat than air and releases it all year round. As a result, the humidity has a warming effect in winter and a cooling effect in summer.
In inland valleys, which benefit less from the balancing effect of the sea, it can be particularly cold in winter because the cold air, which is denser than warm, remains there. Under these conditions, on February 10, 1982 in Edgmond in Shropshire, the lowest temperature ever recorded in England and Wales was recorded at −26.1 ° C.
The warmest winter temperatures occur particularly on the leeward side of mountain ranges. This happens when wet south or south-westerly winds drop after passing the mountains and warm up in the process. In rare cases it can be up to 18 ° C in winter in these areas. This phenomenon is particularly common in Aberdeenshire , despite the low amount of sunshine.
Usually July is the warmest month. The highest temperatures are usually measured some distance from the ocean in the southern, eastern and central areas, where it can be up to 35 ° C.
Weather extremes
While the UK is not known for its weather extremes , these do occur occasionally. In the winter of 1982, for example, it was colder on a few days than in Moscow , while it was particularly dry for three consecutive years in the mid-1970s. This was most pronounced in 1976 when the country suffered from water scarcity. These extreme weather conditions are caused by blocking low pressure zones that do not seem to move for several weeks.
Heavy rain occasionally leads to severe flooding. One of the worst events of this kind happened on 15/16. August 1952 in Lynmouth . The " Lynmouth Disaster " killed 34 people and destroyed 38 buildings. The biggest flood disaster was the Dutch storm flood of 1953, which also affected the British North Sea coast. A strong storm from the Atlantic circled Scotland and pulled down the east coast of England. The resulting storm surge wave was up to 12 meters high; 307 people were killed. Most of the rain in a single day, 279mm, fell on July 18, 1955 in Martinstown , Dorset .
Hurricane winds mainly occur in the autumn and winter months. The most extreme events of this kind were the Great Storm in October 1987 with 23 deaths and damage amounting to 1.2 billion pounds and the Burns' Day storm (so named because of the birthday of the writer Robert Burns ) in January 1990 with 97 deaths and £ 2 billion in damage.