The state is classified as humid subtropical (Cfa) under the Köppen climate classification. The average annual temperature is 64 °F (18 °C). Temperatures tend to be warmer in the southern part of the state with its proximity to the Gulf of Mexico, while the northern parts of the state, especially in the Appalachian Mountains in the northeast, tend to be slightly cooler. Generally, Alabama has very hot summers and mild winters with copious precipitation throughout the year. Alabama receives an average of 56 inches (1,400 mm) of rainfall annually and enjoys a lengthy growing season of up to 300 days in the southern part of the state. Hailstorms occur occasionally in the spring and summer, but are seldom destructive. Heavy fogs are rare, and are confined chiefly to the coast. Thunderstorms oc