The average annual rainfall - 634 mm. Prevailing wind direction - west, south-west and south. St. Petersburg is one of the largest cities and is the most northerly. Symbol of St. Petersburg - White Nights due to high-latitude position of the city. White nights occur on May 25-26, when the sun sinks beyond the horizon of not more than 9 °, and evening twilight practically coincide with the morning. A total length of the white nights, more than 50 days. End white nights, 16-17 July, the longest day falls on June 21-22 (18 hours 53 min.) To St. Petersburg is characterized by moist, close to maritime climate with moderately warm summer and a rather long moderately cold winter. Average temperature in summer +18 ° C, the average winter temperature - 8 ° C. In dry hot weather the temperature can reach +25 ° C. .. +30 ° C. Winter can be a significant cooling: up to -25 ° C. ..- 30 ° C. The precipitation is 634 mm per year.