Amman's position on the mountains near the Mediterranean climate zone places it under the semi-arid climate classification (Köppen climate: BSh borders on BSk). Summers are moderately long, mildly hot and breezy; however, one or two heat waves may occur during summer. Spring is brief and warm, where highs reach . Spring usually starts between April and May, and lasts about a month. Winter usually starts around the end of November and continues from early to mid-March. Temperatures are usually near or below , with snow occasionally falling once or twice a year. Rain averages about  a year and periodic droughts are common, where most rain falls between November and April. At least 120 days of heavy fog per year is usual. Difference in elevation plays a major role in the different weather conditions experienced in the city: snow may accumulate in the western and northern parts of Amman (an average altitude of  above sea level) while at the same time it could be raining at the city center (elevation of .