When to go?
Zanzibar is only a few degrees south of the equator so there is little seasonal variation in temperature. The average maximum is in the high twenties during the winter months, May to September, and in the low thirties from November through to April.
Rainfall though varies a lot. April and May are the monsoon months and the wettest, with up to 15 inches of rain per month, and many hotels close until mid-June. The “short rains” fall in November and early December, but should not spoil a holiday: you would expect tropical showers, rather than continuous rain.
The driest periods are from mid-June to October, with relatively low humidity and refreshing breezes, and mid-December to February. In January, Zanzibar is hot and, with the approach of the monsoon, it becomes more humid.