Climate averages 1991–2020
Knoxville 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 Knoxville: daytime highs average 26.7°C and nights cool to about 16.8°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 90 mm of rain on roughly 8 days, which makes September a wet month (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 26 min on an average September day.
The nearest other city in this atlas is Asheville (130 km away). In September its highs average 24.2°C, 2.5°C cooler than Knoxville, with 95 mm of rain.
Among the 498 cities listed in the United States, Knoxville ranks joint 250th of 498 for the warmest September highs and joint 340th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Knoxville is 0.2°C cooler than that mean.
From September to October, average highs fall by 5.8°C to 20.9°C, and monthly rainfall falls from 90 mm to 74 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
Knoxville climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 8.3°C-0.6°C | -0.6°C | 111 | 10.7 | 10.010 h |
| February | 10.6°C0.8°C | 0.8°C | 110 | 10.9 | 10.911 h |
| March | 15.0°C4.2°C | 4.2°C | 123 | 12.2 | 11.912 h |
| April | 20.0°C8.8°C | 8.8°C | 109 | 10.9 | 13.113 h |
| May | 24.1°C13.8°C | 13.8°C | 94 | 11.7 | 14.014 h |
| June | 28.3°C18.3°C | 18.3°C | 93 | 13.2 | 14.615 h |
| July | 29.8°C20.5°C | 20.5°C | 119 | 14.8 | 14.314 h |
| August | 29.4°C19.9°C | 19.9°C | 86 | 11.4 | 13.514 h |
| September, selected | 26.7°C16.8°C | 16.8°C | 90 | 8.3 | 12.412 h |
| October | 20.9°C10.5°C | 10.5°C | 74 | 7.7 | 11.311 h |
| November | 14.6°C4.5°C | 4.5°C | 96 | 8.9 | 10.310 h |
| December | 9.9°C1.2°C | 1.2°C | 117 | 10.6 | 9.810 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
- Asheville in SeptemberUnited States · 130 kmHigh 24.2°C · Low 14.8°C · 95 mm rain
- East Chattanooga in SeptemberUnited States · 156 kmHigh 27.4°C · Low 18.0°C · 99 mm rain
- Chattanooga in SeptemberUnited States · 162 kmHigh 27.5°C · Low 18.1°C · 99 mm rain
- Johns Creek in SeptemberUnited States · 216 kmHigh 27.4°C · Low 18.5°C · 91 mm rain
- Roswell in SeptemberUnited States · 219 kmHigh 27.1°C · Low 18.2°C · 91 mm rain
- Murfreesboro in SeptemberUnited States · 223 kmHigh 27.7°C · Low 18.0°C · 85 mm rain
- Athens, United States in SeptemberUnited States · 228 kmHigh 27.9°C · Low 18.6°C · 92 mm rain
- Sandy Springs in SeptemberUnited States · 230 kmHigh 27.2°C · Low 18.2°C · 92 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 Knoxville) is explained once on the Knoxville year overview and on the Sources, method and limits page.