South East England combines the highest average daytime temperatures found in the British Isles with the highest sunshine averages on the British mainland. This means that the coastal resort towns of East and West Sussex enjoy more hours of sunshine that anywhere else in Britain.
Rainfall is below average with the heaviest precipitation on the South Downs with 950 mm (37 in) of rainfall per year. The close proximity of Sussex to the Continent of Europe, results in cold spells in winter and hot, humid weather in summer.
The climate of the coastal districts is strongly influenced by the sea, which, because of its tendency to warm up slower than land, can result in cooler temperatures than inland in the summer. In the autumn months, the coast sometimes has higher temperatures. Rainfall during the summer months is mainly from thunderstorms and thundery showers; from January to March the heavier rainfall is due to prevailing south-westerly frontal systems.
The coast has consistently more sunshine than the inland areas: sea breezes, blowing off the sea, tend to clear any cloud from the coast. However, in winter the east winds can be as cold as further inland