Weather in São Paulo in September

Prime time. September is about as good as São Paulo gets. Highs average 27 °C, lows 13.8 °C, and rain falls on 10 days — nothing in the month is working against you.

September ranks 5 of 12 in São Paulo: past the worst of the year but short of August, 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: 8 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest September day reached 37.6 °C and the coldest night fell to 2.5 °C, and the wettest single day dropped 57 mm — roughly 84% of the month's rain in one day.

September is moderately variable: 14 mm in the driest year against 177 mm in the wettest, around an average of 68 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 9.6 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 73%.

How September sits in the year

Temperatures hold steady either side: 24.6 °C in August, 27 here, 28 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

11.9 hours of daylight, gaining 0.7 hours across the month. That is between São Paulo's extremes of 13.6 and 10.7 hours, so days are long enough not to constrain the plan.

An inland climate

Despite being inland, the year stays fairly even: 16.8 °C between the year's warmest afternoons and coldest nights. At 769 m the air is thin enough to matter — sun that burns faster than the temperature suggests, and nights that cool off quickly.

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 São Paulo versus nearby

If São Paulo is one option among several, the nearby comparison is worth making. Curitiba is close enough to be a coin toss — 4.1 °C cooler, 3 days more rain. Rio de Janeiro is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

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

Every month in São Paulo

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