There are four main climatic zones: (1) the coastal area and immediate hinterland, where conditions are tropical, with temperatures averaging about 27° C (81° F ), rainfall varying from 100 to 193 cm (40 to 76 in), and high humidity; (2) the central plateau, which is hot and dry, with rainfall from 50 to 76 cm (20 to 30 in), although with considerable daily and seasonal temperature variations; (3) the semitemperate highland areas, where the climate is healthy and bracing; and (4) the high, moist lake regions. There is little seasonal variation in the Lake Victoria area, but the eastern sections average only 75–100 cm (30–40 in) of rain, while the western parts receive 200–230 cm (80–90 in). A small area north of Lake Niassa receives 250 cm (100 in) of rain. There are two rainy seasons in the north, from November to December and from March through May. In the south there is one rainy season, from November to March.
The climate on the islands is tropical, but the heat is tempered by sea breezes that are constant throughout the year, except during the rainy seasons. The seasons are well defined. From December to March, when the northeast monsoon blows, it is hot and comparatively dry. The heavy rains fall in April and May,
and the lesser in November and December. It is coldest and driest from June to October, during the southwest monsoon.