Although Shenzhen is situated about a degree south of the Tropic of Cancer, due to the Siberian anticyclone it has a warm, monsoon-influenced, humid subtropical climate. Winters are mild and relatively dry, due in part to the influence of the South China Sea, and frost is very rare; it begins dry but becomes progressively more humid and overcast. However, fog is most frequent in winter and spring, with 106 days per year reporting some fog. Early spring is the cloudiest time of year, and rainfall begins to dramatically increase in April; the rainy season lasts until late September to early October. The monsoon reaches its peak intensity in the summer months, when the city also experiences very humid, and hot, but moderated, conditions; there are only 2.4 days of 35 °C (95 °F)+ temperatures.The region is prone to torrential rain as well, with 9.7 days that have 50 mm (1.97 in) or more of rain, and 2.2 days of at least 100 mm (3.94 in).The latter portion of autumn is dry. The annual precipitation averages at around 1,970 mm (78 in), some of which is delivered in typhoons that strike from the east during summer and early autumn. Extreme temperatures have ranged from 0.2 °C (32 °F) on 11 February 1957 to 38.7 °C (102 °F) on 10 July 1980.