Tanzania has a tropical climate but has regional variations due to topography. In the highlands, temperatures range between 10 and 20 °C (50 and 68 °F) during cold and hot seasons respectively.
The rest of the country has temperatures rarely falling lower than 20 °C (68 °F). The hottest period extends between November and February (25–31 °C or 77.0–87.8 °F) while the coldest period occurs between May and August (15–20 °C or 59–68 °F).
Seasonal rainfall is driven mainly by the migration of the Intertropical Convergence Zone. It migrates southwards through Tanzania in October to December, reaching the south of the country in January and February, and returning northwards in March, April, and May. This causes the north and east of Tanzania to experience two distinct wet periods – the short rains (or “Vuli”) in October to December and the long rains (or “Masika”) from March to May – while the southern, western, and central parts of the country experience one wet season that continues October through to April or May.
The onset of the long rains averages 25 March and the cessation averages 21 May. A warmer-than-normal South Atlantic Ocean coupled with a cooler-than-normal Eastern Indian Ocean often causes the onset to be delayed.
Of the land area, 84.1% has a tropical wet and dry/ savanna climate (Aw), 6.9% has a semi-arid/ steppe climate (BS), 9% has a temperate/ mesothermal climate with dry winters (Cw).
Of the population, 80.5% live in a tropical wet and dry/ savanna climate (Aw), 9.5% live in a semi-arid/ steppe climate (BS), 10% live in a temperate/ mesothermal climate with dry winters (Cw)