Alter do Chão weather in December
December in Alter do Chão: sweltering, soaked, with muggy air — a gamble, with 25 rainy days.
Updated September 2026 · climate normals from ERA5 reanalysis
#8 of 12 months in Alter do Chão · #906 of 1413 destinations to visit in December · comfort 63/100 (tier C)
- Days
- 31°C
- Nights
- 26°C
- Wet days
- 25
- Sun
- 9.4 h
- Humidity
- 78%
- Daylight
- 12 h
Traveller notes on Alter do Chão in December
Other months in Alter do Chão
Amazon-region forum threads describe January as squarely within what locals call the Amazonian 'winter' - the wet season - with genuinely heavy rain possible, though posters were consistent that it's very unusual for rain to fall the entire day; sun typically breaks through at some point. That said, one thread specifically warned that during the peak of the rainy season the surrounding area can flood, and recommended the dry season (roughly July through December, aligned with the Southern Hemisphere's drier months) instead for anyone prioritizing accessible trails and beaches over the lush, high-water river scenery January brings.
Forum posters describe September as squarely inside the Amazon's dry season - locally called 'summer,' running roughly July to December - which is also when Alter do Chao's famous river-sand beaches along the Tapajos emerge as water levels drop. Visitor reports from within this dry stretch describe delightful, warm conditions and calm, low water levels ideal for beach time and swimming, in contrast to the wetter 'winter' months when the river rises and submerges the beaches entirely. Posters treat the dry season generally, and September specifically, as the reliable window to actually see and enjoy the riverside beaches this destination is known for, rather than a hit-or-miss gamble on water levels.
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Alter do Chão climate normals — December
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Alter do Chão in December
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, Summer holidays in Brazil, school holidays in 3 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).
Fair weatherAlter do Chão's weather peaks July–September, best around August.
Best weatherFair weatherToughest weather
What's on in Alter do Chão in December
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.
- Season
Wet season
MonsoonRisk25 rainy days and about 316 mm in the month — the real kind of rainy season, not afternoon showers.
from the climate normals
Where is Alter do Chão?
Alter do Chão in December — FAQ
- Is December a good time to visit Alter do Chão?
- December in Alter do Chão: sweltering, soaked, with muggy air — a gamble, with 25 rainy days. It ranks #8 of 12 months for Alter do Chão on SeasonMap's comfort score (63/100).
- What is the weather like in Alter do Chão in December?
- In December, Alter do Chão averages a daily high of 30.9°C and a low of 25.5°C, with about 316 mm of rain over roughly 24.8 rainy days.
- What is the air quality in Alter do Chão in December?
- Alter do Chão has a mean US Air Quality Index of about 52 in December.