Weather in Zanzibar in May

Shoulder season. May is shoulder season in Zanzibar — cheaper, quieter, and a genuine gamble. You should expect rain on 20 days of the month, which is more days wet than dry.

May ranks 8 of 12 in Zanzibar: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain on 20 of the month's 31 days, 6 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Pack for 28.4 °C days and 26.2 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average May reaches 30 °C; the day barely swings — 2.1 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest May day reached 30.5 °C and the coldest night fell to 24 °C, and the wettest single day dropped 69 mm — roughly 37% of the month's rain in one day.

May is moderately variable: 16 mm in the driest year against 448 mm in the wettest, around an average of 186 mm. Roughly two Mays in three land near that average, and the third does something else entirely.

Wind sits around 20.5 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 79%, high enough to notice on the warm days without dominating them.

How May sits in the year

Temperatures hold steady either side: 29.2 °C in April, 28.4 here, 27.6 in June. Nothing about the timing within the month matters much. Rain is the thing that moves: June brings 13 days less of it, so pushing the dates later buys drier weather.

Daylight in May

Zanzibar sits close enough to the equator that daylight barely moves all year — 11.8 hours in May, against a range of just 0.7 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

Sea temperature

The sea sits at about 28.3 °C in May — warm enough that the water offers no relief from the heat. The sea peaks at 29.5 °C in March and bottoms out at 25.6 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

May in Zanzibar versus nearby

If Zanzibar is one option among several, the nearby comparison is worth making. Dar es Salaam is close enough to be a coin toss — within a degree on temperature, 3 days less rain. Mombasa is the weaker option in May — 2.1 °C warmer, 3 days more rain.

So: May is a compromise. July is 35 points better and is what Zanzibar is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Zanzibar

See all twelve months in Zanzibar, or where else to go in May.