Khartoum features a hot desert climate (Köppen climate classification ''BWh'') with a dry season occurring during winter, typical of the Saharo-Sahelian zone, which marks the progressive passage between the Sahara Desert's vast arid areas and the Sahel's vast semi-arid areas. The climate is extremely dry for most of the year, with about eight months when average rainfall is lower than . The very long dry season is itself divided into a warm, very dry season between November and February, as well as a very hot, dry season between March and May. During this part of the year, hot, dry continental trade winds from deserts, such as the harmattan, sweep over the region ; the weather is stable and very dry.