Weather in Rio de Janeiro in September

Prime time. September is about as good as Rio de Janeiro gets. Highs average 26.4 °C, lows 19.7 °C, and rain falls on 10 days — nothing in the month is working against you.

September ranks 5 of 12 in Rio de Janeiro: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain on 10 days, 2 of them heavy. Enough to need a plan B, not enough to need a plan around it. 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: 5 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest September day reached 36.9 °C and the coldest night fell to 15.6 °C, and the wettest single day dropped 66 mm — roughly 96% of the month's rain in one day.

September is moderately variable: 13 mm in the driest year against 164 mm in the wettest, around an average of 69 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 11.3 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 77%, high enough to notice on the warm days without dominating them.

How September sits in the year

Temperatures hold steady either side: 25.7 °C in August, 26.4 here, 27.1 in October. Nothing about the timing within the month matters much.

Daylight in September

11.9 hours of daylight, gaining 0.6 hours across the month. That is between Rio de Janeiro's extremes of 13.5 and 10.7 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 22.3 °C in September — comfortable for a proper swim. The sea peaks at 26.7 °C in March and bottoms out at 22.3 °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 Rio de Janeiro versus nearby

If Rio de Janeiro is one option among several, the nearby comparison is worth making. Belo Horizonte is close enough to be a coin toss — 3.7 °C warmer, 4 days less rain. São Paulo is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: September works, with July the better month by 8 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Rio de Janeiro

See all twelve months in Rio de Janeiro, or where else to go in September.