Although Zambia lies within the tropics, much of it has a pleasant climate because of the altitude. There are wide seasonal variations in temperature and rainfall. October is the hottest month. The main rainy season starts in mid-November, with heavy tropical storms lasting well into April. The northern and northwestern provinces have an annual rainfall of about 125 cm (50 in), while areas in the far south have as little as 75 cm (30 in). May to mid-August is the cool season, after which temperatures rise rapidly. September is very dry. Daytime temperatures may range from 23° to 31°c (73–88°f), dropping at night to as low as 5°c (41°f) in June and July.