Climate averages 1991–2020
Rio Branco weather
in September.
A hot, moderately wet month: the warmest and the joint 4th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a hot month in Rio Branco: daytime highs average 32.4°C and nights cool to about 22.7°C. By daytime temperature it is the warmest month of the year.
Expect about 76 mm of rain on roughly 12 days, which makes September a moderately wet month (the joint 4th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 02 min on an average September day.
The nearest other city in this atlas is Riberalta (224 km away). In September its highs average 32.2°C, about as warm as Rio Branco, with 84 mm of rain.
Among the 448 cities listed in Brazil, Rio Branco ranks joint 57th of 448 for the warmest September highs and joint 268th of 448 for the driest September (rainfall, lowest first). The mean September high of those 448 cities is 27.5°C; Rio Branco is 4.9°C warmer than that mean.
From September to October, average highs fall by 0.9°C to 31.5°C, and monthly rainfall rises from 76 mm to 137 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Rio Branco climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 29.4°C22.9°C | 22.9°C | 255 | 27.6 | 12.613 h |
| February | 29.2°C22.8°C | 22.8°C | 243 | 25.3 | 12.412 h |
| March | 29.2°C22.8°C | 22.8°C | 249 | 27.2 | 12.212 h |
| April | 28.9°C22.4°C | 22.4°C | 160 | 22.7 | 11.912 h |
| May | 28.4°C21.6°C | 21.6°C | 76 | 15.4 | 11.712 h |
| June | 28.9°C20.9°C | 20.9°C | 30 | 6.8 | 11.612 h |
| July | 30.4°C20.4°C | 20.4°C | 21 | 4.2 | 11.612 h |
| August | 32.1°C21.4°C | 21.4°C | 38 | 6.3 | 11.812 h |
| September, selected | 32.4°C22.7°C | 22.7°C | 76 | 11.9 | 12.012 h |
| October | 31.5°C23.0°C | 23.0°C | 137 | 19.5 | 12.312 h |
| November | 30.1°C22.9°C | 22.9°C | 199 | 22.9 | 12.613 h |
| December | 29.5°C23.0°C | 23.0°C | 246 | 26.3 | 12.713 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Riberalta in SeptemberBolivia · 224 kmHigh 32.2°C · Low 23.1°C · 84 mm rain
- Puerto Maldonado in SeptemberPeru · 328 kmHigh 30.8°C · Low 22.0°C · 119 mm rain
- Porto Velho in SeptemberBrazil · 449 kmHigh 32.6°C · Low 23.8°C · 103 mm rain
- Ariquemes in SeptemberBrazil · 522 kmHigh 33.1°C · Low 23.3°C · 86 mm rain
- Cruzeiro do Sul in SeptemberBrazil · 595 kmHigh 30.6°C · Low 22.4°C · 109 mm rain
- Cusco in SeptemberPeru · 601 kmHigh 16.2°C · Low 6.6°C · 37 mm rain
- Trinidad in SeptemberBolivia · 626 kmHigh 31.2°C · Low 22.2°C · 106 mm rain
- Ji Paraná in SeptemberBrazil · 649 kmHigh 33.3°C · Low 23.2°C · 80 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Rio Branco) is explained once on the Rio Branco year overview and on the Sources, method and limits page.