Tanzania is hot throughout the year and is humid on the coast and dry on the central plateau. The heavy rains last from March to June and can make unsealed road travel difficult. The hot, dry weather in January and February attracts the most tourists. The best time to visit the Serengeti is from January to March when the grazers are calving and there are plenty of lion around, or to witness the wildebeest migration to and from Kenya which occurs at the onset of the dry season and again with the first rains, usually the beginning of June and mid-November.
Zanzibar has a warm climate year-round and its coastal resorts are tempered by sea breezes. The island is best avoided in April and May which is the rainy season.
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). Annual average temperature is 20 °C (68.0 °F).