Weather in Zanzibar in September

Prime time. If you get to pick your dates, September is the one. Highs average 27.8 °C, lows 24.6 °C, and rain falls on 5 days — nothing in the month is working against you.

September ranks 3 of 12 in Zanzibar. Only July scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain falls on only 5 days, so an itinerary with no wet-weather fallback is a reasonable risk. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

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 September reaches 30 °C; the day barely swings — 3.2 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 29.2 °C and the coldest night fell to 23.1 °C, and the wettest single day dropped 26 mm — roughly 118% of the month's rain in one day.

This is the volatile part. September rainfall has ranged from 1 mm to 80 mm across the twenty years measured — a 79 mm spread around an average of 22 mm. The average is real but almost no individual September looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind sits around 18.3 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity is unremarkable at 74%.

How September sits in the year

Temperatures hold steady either side: 27.2 °C in August, 27.8 here, 28.7 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 7 days more of it, so the earlier half of a flexible trip is the safer half.

Daylight in September

Zanzibar sits close enough to the equator that daylight barely moves all year — 12.1 hours in September, 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 25.9 °C in September — warm enough to stay in as long as you like. 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

Busy. Popular without being frantic; book the things you care about, improvise the rest.

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

September 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, the same number of rain days. Mombasa is the weaker option in September — 4 °C warmer, 3 days more rain.

So: September is effectively as good as it gets here — 6 points behind July, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Zanzibar

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