January and February are the coldest months of the year , with an average temperature of 0,1 Â C and 0,4 Â C. July and August are the hottest months , with an average temperature of 17,8 Â C ( 63 Â F ) and 17,2 Â C. The average annual rainfall is about 438 millimetres . The rain occurs usually from May to September . January and February are the coldest months of the year , with an average temperature of 0.1 Â C and 0.4 Â C. July and August are the hottest months , with an average temperature of 17.8 Â C ( 63 Â F ) and 17.2 Â C. The average annual precipitation is close to 438 millimetres with rain occurring usually from May to September .