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. Temperatures usually do not reach freezing points, especially in coastal areas. However, the temperature is mainly warm to mediate temperatures.
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.
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. These are some of the wettest locations in Britain. 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, but is rare. Hail, although uncommon, can happen any time throughout the year.
The prevailing winds over the British Isles are from the south-west, and winds are strongest on coasts that face the Atlantic. Generally, the coast tends to be windier than inland areas; and the west tends to be windier than the east.