The climate of Great Britain, influenced by the Atlantic Ocean, is temperate and humid, with relatively small temperature variations between winter and summer. The weather, however, is variable, with frequent changes from day to day or even in the same day.

The average temperatures in the plains are above freezing (0 °C or 32 °F) also in January, when they hover around 4/5 °C (39/41 °F) in the main cities, and reach 6 °C (43 °F) in the south-western tip of the country; in July they range between 12 °C (53.5 °F) in northern Scotland and 18.5 °C (65.5 °F) in the London area.

Precipitation is frequent throughout the country, but is more frequent and abundant in the north and in the west. For example, in the west of Scotland it reaches 1,500 millimetres (60 inches) per year, with about 200 days of rain (more than one day out of two!), while in Manchester, 800 mm (31.5 in) of rain fall in 141 days; in Plymouth, on the southwest coast, 1,000 mm (40 in) of rain fall in 142 days; the southeast is less rainy: in London only 600 mm (23.5 in) of rain fall in a year, distributed in 109 days.



Scotland map
In Scotland, the weather is very cool, damp, rainy and windy for most of the year.
Rainfall is more abundant on the western side and on the highlands, where it even exceeds 1,500 mm (60 in) per year, while it's less abundant on the eastern side, where it drops to 600/700 mm (24/28 in): so Glasgow is rainier than Edinburgh. However, the rains are common everywhere, and even in the summer months, there are more than ten days of rain per month on average.
Here is the average precipitation in Glasgow.
Glasgow - Average precipitation

The wind is more common in the western and northern side and in the islands: no coincidence that the main cities (Aberdeen, Dundee, Glasgow, Edinburgh) lie in the eastern or southern side, which are relatively sheltered. However, when the most intense low pressure systems occur, the wind can be strong everywhere.
The Gulf Stream makes winter fairly mild, at least in comparison with other countries located at the same latitude: the average temperature in January and February is around 4/5 °C (39/41 °F). However, the northern location makes Scotland prone to cold winds from Greenland, which can bring snow showers and frosts, especially in the highlands, but usually these periods don't last long, because after a short time the westerlies start to blow again.
In spring, the temperature rises very slowly, so that it's still cold in April, when the maximum temperature is around 10/12 °C (50/54 °F). In return, spring is the relatively sunniest season.
Summer is very cool: the average maximum temperature in July and August ranges from 13 °C (55.5 °F) in the Shetland Islands, to 15/16 °C (59/61 °F) in the north-west, to 18/19 °C (64/66 °F) in Glasgow and Edinburgh. Lows at night are around 10/11 °C (50/52 °F). In Scotland, even summer is a pretty rainy season, and sunshine in mid-summer (July and August) is even rarer than in early summer (June).
Autumn is cold, windy and rainy. The wind in Scotland is frequent, and sometimes can be very strong, especially in autumn and winter.
Here are the average temperatures of Edinburgh:
Edinburgh - Average temperatures
Min (°C)113471011119641
Max (°C)781012151719191713107
Min (°F)343437394550525248433934
Max (°F)454650545963666663555045


In the Highlands of course the weather is colder, and snowfalls often occur in winter. Snow cover duration is remarkable, because the temperature increases slightly in the other seasons. The wind in the Highlands is also more intense and frequent, as generally happens in mountainous regions.
Here for example the temperatures of Glen Ogle, which is located at 565 metres (1,855 feet) above sea level.
Glen Ogle - Average temperatures
Min (°C)-1-2-114688641-1
Max (°C)33471012141412853
Min (°F)302830343943464643393430
Max (°F)373739455054575754464137

At higher altitudes, temperatures are even lower, as can be seen from the data of Cairngorm Mountain, at 1,245 metres (4,085 feet), where there is also a ski lift.
Cairn Gorm - Average temperatures
Min (°C)-6-6-5-3-12442-1-3-5
Max (°C)-1-2-12471097410
Min (°F)212123273036393936302723
Max (°F)302830363945504845393432

Loch Ness

The sky in Scotland is often cloudy, so the sun is rarely seen, however the relatively sunnier month (compared to the length of the days) is May. Here are the average daily sunshine hours in Edinburgh.
Edinburgh - Sunshine

The sea in Scotland is not so cold in winter, at least if we consider the latitude, while it remains cold in summer. Here are the average water temperatures at Aberdeen.
Aberdeen - Sea temperature
Temp (°C)877781113131211108
Temp (°F)464545454652555554525046


Wales map
In Wales the climate is cool and cloudy for most of the year, but in winter it's milder than Scotland, because it's more sheltered from polar air masses, but also from continental air masses which may affect England. The average temperature in January and February is around 5 °C (41 °F). Summer is cool, especially in the northern part: the average in July and August is around 15 °C (59 °F) in the north and 16/17 °C (61/63 °F) in the south; the average maximum temperatures reach 20/22 °C (68/72 °F) in the southernmost cities located in the Bristol Channel (Swansea, Cardiff).


Here are the average temperatures in Cardiff.
Cardiff - Average temperatures
Min (°C)2245811131311853
Max (°C)891114172022221915119
Min (°F)363639414652555552464137
Max (°F)464852576368727266595248

The rains in Wales are frequent throughout the year, and abundant in autumn and winter, while they reach a minimum between April and June.
Here is the average precipitation in Cardiff.
Cardiff - Average precipitation

In Wales too, the sky is often cloudy, however, the sun shines for about 6 hours per day from May to August (which, considering the length of the days, are not many).
Cardiff - Sunshine

The temperature of the sea in Wales is a bit higher than in Scotland, but remains very cool, if not cold, in summer. Here are the average water temperatures at Swansea.
Swansea - Sea temperature
Temp (°C)1099101113151616151311
Temp (°F)504848505255596161595552


England map
In England, the climate is temperate, and it's cool for most of the year.
Here are the average temperatures of Liverpool, located in the west.
Liverpool - Average temperatures
Min (°C)2245811131311853
Max (°C)77912161820191714108
Min (°F)363639414652555552464137
Max (°F)454548546164686663575046

In England, rainfall is more abundant in the north-west and in the south-west, where it exceeds 1,000 mm (40 in) per year.
Here is the average precipitation in Liverpool, where it is at an intermediate level, given that it amounts to 835 mm (33 in) per year.
Liverpool - Average precipitation

Winter in England is cold and cloudy, sometimes foggy, sometimes windy. The average temperatures in this season don't vary much from north to south: in January they are around 4/5 °C (39/41 °F) in Newcastle upon Tyne as in Birmingham, and also in the countryside around London. In Liverpool and Manchester, the average temperatures are similar as well.
In fact, the southernmost regions are the farthest from the pole, but they are also the closest to the European mainland, from which cold air masses of Russian origin can arrive during winter. For this reason, the east side (which includes London) is also more prone to snowfall. However, these snowy or freezing periods are typically short-lived, because here too, as in Scotland, the westerlies tend to come back after a short time.
As we have said, cold air masses reach Scotland from the north and England from the east, so it's not surprising that, in addition to Wales, the mildest area is south-western England (Devon and Cornwall), where the average temperature in January and February hovers around 6 °C (43 °F, see Plymouth). Here snowfalls and frosts are rare.
Here are the average temperatures in Plymouth.
Plymouth - Average temperatures
Min (°C)4456911131312965
Max (°C)9911131618202018151210
Min (°F)393941434852555554484341
Max (°F)484852556164686864595450

On the tip of Cornwall, the island of Scilly and the islets of the English Channel (see Jersey) have microclimates in which the absence of frost permits the growth of subtropical plant species. On the other hand, in the south-west, being so much exposed to the Atlantic currents, rainfall is more abundant.
Here is the average precipitation in Plymouth.
Plymouth - Average precipitation

Spring in England is very cool, and the temperature increases slowly; rainfall is still frequent, but less abundant than in autumn and winter.
Late spring is the sunniest period of the year, despite the almost daily presence of clouds; the wind also reduces its intensity and its frequency. In May, the country is covered with flowers.
June is a nice month: the days are long, nature is in bloom (thanks also to the passion that the British have for gardening), and the temperatures are pleasant. However, there can be, as always, rain and showers.
Unlike in winter, during summer the temperature increases from the north-west to the south-east, so the highest temperatures are found in the area of London. In summer, daytime temperatures range from 18 °C (64 °F) in Newcastle, to 19 °C (66 °F) in Manchester, 20 °C (68 °F) in Birmingham and Cambridge, to 23 °C (73 °F) in the London area. In the south-west, which during winter was the mildest area, summer is cool: lows are around 13 °C (55 °F), and highs around 20 °C (68 °F).
Even in summer, the weather is variable across the country, so that it can change from day to day, or several times during the same day. Southern England is the area most subject to hot periods, in which currents from Spain can bring a taste of Mediterranean summer, and the temperature may even reach 28/32 °C (82/90 °F). These periods, however, do not occur every year, and usually last for a few days.
During summer the rains are more frequent and abundant in the north than in the south: while in Manchester in July there are on average 12 days with rain, in London they are "only" 8.
Here is the average precipitation in London.
London - Average precipitation

Sometimes in summer, thunderstorms can burst, especially in inland and southern areas, often accompanied by wind gusts.
Here are the average temperatures of London.
London - Average temperatures
Min (°C)2246912141411853
Max (°C)881114182123232016118
Min (°F)363639434854575752464137
Max (°F)464652576470737368615246


In Northern England, the sky is often cloudy: in Liverpool and Manchester the sun shines at most for 6 hours a day from May to July; it goes a bit better in the south (see London, Brighton), where it can reach 7 hours.
Manchester - Sunshine

The temperature of the sea in England increases gradually from north to south, so that in August it reaches 15 °C (59 °F) in Liverpool and Newcastle, and 17 °C (63 °F) in the south, as you can see from the average water temperature at Brighton.
Brighton - Sea temperature
Temp (°C)98891113151717161311
Temp (°F)484646485255596363615552

When to go

The best time to visit Britain is summer, from June to August: it's a very cool season in Scotland, and progressively warmer as you head south; it's quite rainy everywhere, but also relatively sunny.
In Scotland, in July and August there is an increase in rainfall and a decrease in sunshine: here the sunniest month is June, which, however, is cooler than the two mid-summer months.
In the whole of Britain, June is a good month: the days are very long, the country is in bloom, there's no shortage of rain and clouds, but they alternate with sunny spells. Also May (which is very cool, and sometimes even cold, especially in the north and in Scotland), often provides an acceptable weather, at least in the second half.
The mid-summer season (July-August) in the centre and south is pleasantly warm, and between showers, the sun can come out.
As mentioned, the sea is cold even in summer: in August the temperature of the Atlantic reaches just 12 °C (53.5 °F) in the Shetlands, 13/14 °C (55/57 °F) in Scotland, 17 °C (63 °F) in the English Channel and in Cornwall.
Since the climate of Great Britain is not characterized by weather extremes, there is no season to be absolutely avoided, although it must be said that late autumn (November and early December) is characterized by very short days, mostly cloudy skies, frequent rains and sometimes strong winds, while the mid-winter period (January-February, and sometimes December) as well as mild periods, can sometimes offer cold periods.

What to pack

In winter: warm clothes, sweater, coat, wind jacket, raincoat. For Scotland and the Highlands, and for cold periods: gloves, hat, scarf.
In summer: clothes for spring and autumn, jacket and sweater, raincoat or umbrella. In the area of London, it's more likely that in some days you can wear light clothing, t-shirt and shorts.

For the climate of Northern Ireland, see the climate of Ireland.