Shanghai has a humid subtropical climate, with an average annual temperature of 15.8 °C (60.4 °F) for urban districts and 15.2–15.7 °C (59.4–60.3 °F) for suburbs. The city experiences four distinct seasons. Winters are chilly and damp—northwesterly winds from Siberia can cause nighttime temperatures to drop below freezing. Each year, there are an average of 6.2 days with snowfall and 2.8 days with snow cover. Summers are hot and humid, and occasional downpours or freak thunderstorms can be expected.