Climate averages 1991–2020
Porto Alegre weather
in September.
A mild, wet month: the 8th warmest and the 11th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Porto Alegre: daytime highs average 21.6°C and nights cool to about 12.8°C. By daytime temperature it is the 8th warmest of the 12 months.
Expect about 146 mm of rain on roughly 11 days, which makes September a wet month (the 11th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 11 h 53 min on an average September day.
The nearest other city in this atlas is Guaíba (13 km away). In September its highs average 21.4°C, about as warm as Porto Alegre, with 146 mm of rain.
Among the 448 cities listed in Brazil, Porto Alegre ranks joint 408th of 448 for the warmest September highs and joint 400th of 448 for the driest September (rainfall, lowest first). The mean September high of those 448 cities is 27.5°C; Porto Alegre is 5.9°C cooler than that mean.
From September to October, average highs rise by 2.2°C to 23.8°C, and monthly rainfall rises from 146 mm to 170 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 Alegre climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 29.2°C20.6°C | 20.6°C | 137 | 14.0 | 13.814 h |
| February | 28.8°C20.6°C | 20.6°C | 128 | 13.5 | 13.213 h |
| March | 27.5°C19.3°C | 19.3°C | 111 | 11.9 | 12.312 h |
| April | 24.9°C16.5°C | 16.5°C | 106 | 9.2 | 11.411 h |
| May | 21.1°C13.2°C | 13.2°C | 107 | 9.2 | 10.611 h |
| June | 19.0°C10.8°C | 10.8°C | 113 | 9.2 | 10.210 h |
| July | 18.4°C9.8°C | 9.8°C | 140 | 10.0 | 10.410 h |
| August | 20.6°C11.0°C | 11.0°C | 120 | 10.2 | 11.011 h |
| September, selected | 21.6°C12.8°C | 12.8°C | 146 | 11.1 | 11.912 h |
| October | 23.8°C15.2°C | 15.2°C | 170 | 12.4 | 12.813 h |
| November | 26.0°C16.8°C | 16.8°C | 122 | 10.9 | 13.614 h |
| December | 28.4°C19.2°C | 19.2°C | 124 | 11.8 | 14.014 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
- Guaíba in SeptemberBrazil · 13 kmHigh 21.4°C · Low 12.8°C · 146 mm rain
- Canoas in SeptemberBrazil · 14 kmHigh 21.7°C · Low 12.8°C · 146 mm rain
- Alvorada in SeptemberBrazil · 15 kmHigh 21.5°C · Low 12.9°C · 147 mm rain
- Viamão in SeptemberBrazil · 21 kmHigh 20.8°C · Low 12.9°C · 147 mm rain
- Gravataí in SeptemberBrazil · 25 kmHigh 21.6°C · Low 12.7°C · 147 mm rain
- São Leopoldo in SeptemberBrazil · 31 kmHigh 21.8°C · Low 12.6°C · 160 mm rain
- Novo Hamburgo in SeptemberBrazil · 41 kmHigh 21.6°C · Low 11.9°C · 160 mm rain
- Sapiranga in SeptemberBrazil · 49 kmHigh 22.3°C · Low 12.8°C · 153 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 Alegre) is explained once on the Porto Alegre year overview and on the Sources, method and limits page.
Canoas and Guaíba lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.