Climate averages 1991–2020
Rio das Ostras weather
in September.
A warm, moderately wet month: the 8th warmest and the 5th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Rio das Ostras: daytime highs average 25.7°C and nights cool to about 18.9°C. By daytime temperature it is the 8th warmest of the 12 months.
Expect about 73 mm of rain on roughly 10 days, which makes September a moderately wet month (the 5th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 11 h 57 min on an average September day.
The nearest other city in this atlas is Macaé (23 km away). In September its highs average 25.4°C, about as warm as Rio das Ostras, with 60 mm of rain.
Among the 448 cities listed in Brazil, Rio das Ostras ranks joint 310th of 448 for the warmest September highs and joint 259th of 448 for the driest September (rainfall, lowest first). The mean September high of those 448 cities is 27.5°C; Rio das Ostras is 1.8°C cooler than that mean.
From September to October, average highs rise by 0.8°C to 26.6°C, and monthly rainfall rises from 73 mm to 108 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 das Ostras climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 29.4°C23.2°C | 23.2°C | 206 | 16.5 | 13.313 h |
| February | 29.8°C23.4°C | 23.4°C | 141 | 12.8 | 12.913 h |
| March | 28.6°C22.8°C | 22.8°C | 172 | 17.6 | 12.212 h |
| April | 27.2°C21.3°C | 21.3°C | 85 | 12.1 | 11.612 h |
| May | 25.1°C19.1°C | 19.1°C | 60 | 9.5 | 11.111 h |
| June | 24.7°C17.9°C | 17.9°C | 31 | 5.9 | 10.811 h |
| July | 24.4°C17.4°C | 17.4°C | 29 | 5.6 | 10.911 h |
| August | 25.0°C17.8°C | 17.8°C | 34 | 6.5 | 11.311 h |
| September, selected | 25.7°C18.9°C | 18.9°C | 73 | 10.0 | 11.912 h |
| October | 26.6°C20.2°C | 20.2°C | 108 | 11.9 | 12.613 h |
| November | 26.8°C21.0°C | 21.0°C | 203 | 17.5 | 13.213 h |
| December | 28.4°C22.4°C | 22.4°C | 222 | 19.0 | 13.513 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
- Macaé in SeptemberBrazil · 23 kmHigh 25.4°C · Low 19.2°C · 60 mm rain
- São Pedro da Aldeia in SeptemberBrazil · 38 kmHigh 23.9°C · Low 19.7°C · 56 mm rain
- Cabo Frio in SeptemberBrazil · 41 kmHigh 23.8°C · Low 20.0°C · 47 mm rain
- Araruama in SeptemberBrazil · 56 kmHigh 23.9°C · Low 19.7°C · 74 mm rain
- Nova Friburgo in SeptemberBrazil · 66 kmHigh 23.8°C · Low 15.2°C · 117 mm rain
- Saquarema in SeptemberBrazil · 68 kmHigh 24.5°C · Low 19.3°C · 58 mm rain
- Itaboraí in SeptemberBrazil · 97 kmHigh 25.9°C · Low 17.4°C · 82 mm rain
- Maricá in SeptemberBrazil · 100 kmHigh 26.0°C · Low 19.2°C · 61 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 das Ostras) is explained once on the Rio das Ostras year overview and on the Sources, method and limits page.