Weather in Mombasa in September

A good month. September is a solid month to be in Mombasa. Highs average 31.8 °C, lows 22.5 °C, and rain falls on 8 days — nothing in the month is working against you.

September ranks 4 of 12 in Mombasa: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain on 8 days, 1 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 31.8 °C days and 22.5 °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: 29 days top 30 °C, making the heat continuous rather than occasional. Across the twenty years measured, the hottest September day reached 34.3 °C and the coldest night fell to 19.8 °C, and the wettest single day dropped 29 mm — roughly 76% of the month's rain in one day.

September is moderately variable: 5 mm in the driest year against 79 mm in the wettest, around an average of 38 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 14.2 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 71%.

How September sits in the year

Temperatures hold steady either side: 30.6 °C in August, 31.8 here, 32.7 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 5 days more of it, so the earlier half of a flexible trip is the safer half.

Daylight in September

Mombasa sits close enough to the equator that daylight barely moves all year — 12.1 hours in September, against a range of just 0.5 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 29.4 °C in April and bottoms out at 25.7 °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 Mombasa versus nearby

If Mombasa is one option among several, the nearby comparison is worth making. Zanzibar is a better bet in September — 4 °C cooler, 3 days less rain. Dar es Salaam is a better bet in September — 3 °C cooler, 3 days less rain.

So: September works, with July the better month by 11 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Mombasa

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