Climate averages 1991–2020
Porto Velho weather
in September.
A hot, wet month: the 2nd warmest and the 4th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a hot month in Porto Velho: daytime highs average 32.6°C and nights cool to about 23.8°C. By daytime temperature it is the 2nd warmest of the 12 months.
Expect about 103 mm of rain on roughly 17 days, which makes September a wet month (the 4th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 03 min on an average September day.
The nearest other city in this atlas is Ariquemes (159 km away). In September its highs average 33.1°C, 0.6°C warmer than Porto Velho, with 86 mm of rain.
Among the 448 cities listed in Brazil, Porto Velho ranks 55th of 448 for the warmest September highs and 346th of 448 for the driest September (rainfall, lowest first). The mean September high of those 448 cities is 27.5°C; Porto Velho is 5.0°C warmer than that mean.
From September to October, average highs fall by 0.8°C to 31.7°C, and monthly rainfall rises from 103 mm to 178 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
Porto Velho climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 29.6°C23.4°C | 23.4°C | 303 | 28.6 | 12.613 h |
| February | 29.4°C23.3°C | 23.3°C | 318 | 27.0 | 12.412 h |
| March | 29.3°C23.4°C | 23.4°C | 328 | 29.4 | 12.212 h |
| April | 29.2°C23.3°C | 23.3°C | 228 | 26.4 | 11.912 h |
| May | 29.1°C22.9°C | 22.9°C | 133 | 21.4 | 11.712 h |
| June | 29.7°C22.3°C | 22.3°C | 43 | 9.5 | 11.612 h |
| July | 31.3°C21.9°C | 21.9°C | 22 | 4.7 | 11.712 h |
| August | 33.0°C22.9°C | 22.9°C | 42 | 7.5 | 11.812 h |
| September, selected | 32.6°C23.8°C | 23.8°C | 103 | 16.7 | 12.012 h |
| October | 31.7°C23.9°C | 23.9°C | 178 | 23.2 | 12.312 h |
| November | 30.3°C23.7°C | 23.7°C | 245 | 26.2 | 12.513 h |
| December | 29.7°C23.5°C | 23.5°C | 298 | 28.7 | 12.613 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
- Ariquemes in SeptemberBrazil · 159 kmHigh 33.1°C · Low 23.3°C · 86 mm rain
- Ji Paraná in SeptemberBrazil · 319 kmHigh 33.3°C · Low 23.2°C · 80 mm rain
- Riberalta in SeptemberBolivia · 343 kmHigh 32.2°C · Low 23.1°C · 84 mm rain
- Cacoal in SeptemberBrazil · 401 kmHigh 33.3°C · Low 23.0°C · 90 mm rain
- Rio Branco in SeptemberBrazil · 449 kmHigh 32.4°C · Low 22.7°C · 76 mm rain
- Coari in SeptemberBrazil · 527 kmHigh 30.2°C · Low 24.6°C · 123 mm rain
- Vilhena in SeptemberBrazil · 603 kmHigh 30.8°C · Low 20.9°C · 84 mm rain
- Tefé in SeptemberBrazil · 606 kmHigh 30.1°C · Low 23.8°C · 142 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 Porto Velho) is explained once on the Porto Velho year overview and on the Sources, method and limits page.