Summers are warm and sometimes humid with average high temperatures of  and lows of . Winters are cool with average high temperatures of  and lows of . Spring and autumn are generally chilly to mild. Berlin's built-up area creates a microclimate, with heat stored by the city's buildings and pavement. Temperatures can be  higher in the city than in the surrounding areas. Annual precipitation is  with moderate rainfall throughout the year. Berlin and the surrounding state of Brandenburg are the warmest and driest regions in Germany. Snowfall mainly occurs from December through March. The hottest month in Berlin was July 1834, with a mean temperature of  and the coldest was January 1709, with a mean temperature of . The wettest month on record was July 1907, with  of rainfall, whereas the driest were October 1866, November 1902, October 1908 and September 1928, all with  of rainfall.