SeasonMapAlter do Chão weather in September
Brazil
September in Alter do Chão: hot, a little rain, with clean air — one of the best months to visit.
#1 of 12 months in Alter do Chão · #248 of 1383 destinations to visit in September · comfort 89/100 (tier A)
Updated September 2026 · climate normals from ERA5 reanalysis
Traveller notes on Alter do Chão in September
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Alter do Chão climate normals — September
| Daytime high | 32°C / 89°F | 🥵 hot |
|---|---|---|
| Nighttime low | 28°C / 82°F | |
| Rainfall | 33 mm / 1.3 in | 🌦 some rain |
| Rainy days | 6 days | |
| Humidity | 68% | 💧 humid |
| Dew point | 23°C / 74°F | |
| Sunshine | 10.9 h/day | |
| Daylight | 12.1 h | |
| Wind | 16 km/h / 10 mph | |
| Air quality (US AQI) | 43 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Alter do Chão in September
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
Peak crowdsRiver beaches emerge, Festival do Sairé, school holidays in 2 of the markets that fill it(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Alter do Chão's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Best weatherAlter do Chão's weather peaks July–September.
September includes Festival do Sairé.
Best weatherFair weatherToughest weather
What's on in Alter do Chão in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Season
River beaches emerge
1 Aug – 31 Jan · usuallyHigh waterCrowdedThe Tapajós drops from August and the white sandbanks in front of the village come back out of the water. By September you can wade to the Ilha do Amor, and in a hard year walk to it.
- Festival
Festival do Sairé
17–21 SepMajor festivalCrowdedBook earlyFive days of mast-raising, church procession and the Botos contest, where two dolphin teams sing and dance at each other in a purpose-built arena. Santarém has now fixed it to the third week of September. Source ↗
Where is Alter do Chão?
Alter do Chão in September — FAQ
- Is September a good time to visit Alter do Chão?
- September in Alter do Chão: hot, a little rain, with clean air — one of the best months to visit. It ranks #1 of 12 months for Alter do Chão on SeasonMap's comfort score (89/100).
- What is the weather like in Alter do Chão in September?
- In September, Alter do Chão averages a daily high of 31.6°C and a low of 27.8°C, with about 32.5 mm of rain over roughly 6 rainy days.
- What is the air quality in Alter do Chão in September?
- Alter do Chão has a mean US Air Quality Index of about 43 in September.