London has a temperate climate with regular, light rain throughout the year. July is the warmest month, with an average temperature at Greenwich of 13.6 ° C to 22.8 ° C. The coldest month is January, with an average of 2.4 ° C to 7.9 ° C. The average annual rainfall is 583.6 mm, and February is normally the driest month. Snow is uncommon in London itself, although there is regular snow in the surrounding area; this is because the extra heat the big city generates makes the city about 5 ° C warmer than surrounding areas in winter.