Climate averages 1991–2020
Roswell weather
in September.
A warm, wet month: the 4th warmest and the 3rd driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Roswell: daytime highs average 27.1°C and nights cool to about 18.2°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 91 mm of rain on roughly 9 days, which makes September a wet month (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 25 min on an average September day.
The nearest other city in this atlas is Sandy Springs (11 km away). In September its highs average 27.2°C, about as warm as Roswell, with 92 mm of rain.
Among the 498 cities listed in the United States, Roswell ranks joint 238th of 498 for the warmest September highs and joint 343rd of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Roswell is 0.2°C warmer than that mean.
From September to October, average highs fall by 5.3°C to 21.8°C, and monthly rainfall falls from 91 mm to 86 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
Roswell climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 10.3°C1.4°C | 1.4°C | 116 | 10.4 | 10.210 h |
| February | 12.5°C2.9°C | 2.9°C | 117 | 10.1 | 10.911 h |
| March | 16.6°C6.3°C | 6.3°C | 120 | 10.3 | 12.012 h |
| April | 21.2°C10.4°C | 10.4°C | 102 | 9.6 | 13.013 h |
| May | 25.5°C15.2°C | 15.2°C | 85 | 9.8 | 13.914 h |
| June | 29.0°C19.5°C | 19.5°C | 104 | 13.6 | 14.414 h |
| July | 30.5°C21.5°C | 21.5°C | 104 | 14.6 | 14.214 h |
| August | 30.0°C21.1°C | 21.1°C | 104 | 12.6 | 13.413 h |
| September, selected | 27.1°C18.2°C | 18.2°C | 91 | 8.6 | 12.412 h |
| October | 21.8°C12.3°C | 12.3°C | 86 | 7.2 | 11.411 h |
| November | 16.0°C6.5°C | 6.5°C | 99 | 8.5 | 10.410 h |
| December | 11.5°C3.0°C | 3.0°C | 117 | 10.3 | 9.910 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
- Sandy Springs in SeptemberUnited States · 11 kmHigh 27.2°C · Low 18.2°C · 92 mm rain
- Johns Creek in SeptemberUnited States · 15 kmHigh 27.4°C · Low 18.5°C · 91 mm rain
- Atlanta in SeptemberUnited States · 31 kmHigh 27.3°C · Low 18.1°C · 89 mm rain
- South Fulton in SeptemberUnited States · 56 kmHigh 27.6°C · Low 18.7°C · 88 mm rain
- Athens, United States in SeptemberUnited States · 91 kmHigh 27.9°C · Low 18.6°C · 92 mm rain
- East Chattanooga in SeptemberUnited States · 142 kmHigh 27.4°C · Low 18.0°C · 99 mm rain
- Chattanooga in SeptemberUnited States · 143 kmHigh 27.5°C · Low 18.1°C · 99 mm rain
- Macon in SeptemberUnited States · 148 kmHigh 29.3°C · Low 19.7°C · 91 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 Roswell) is explained once on the Roswell year overview and on the Sources, method and limits page.
Johns Creek lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.