Knoxville weather in September: Knoxville, Tennessee: normal highs, lows, rain and records for September
Knoxville in September has a normal high of 83°F and a normal low of 61°F, a daily mean of 72°F, falling from 86°F on the 1st to 78°F by the 30th. Measurable precipitation falls on 8 days in a normal September, 3.49 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 28°C and low of 16°C, 89 mm of precipitation in September.
- NOAA stationKnoxville Airport
- Station IDUSW00013891
- Location35.82°N 83.99°W
- Elevation962 ft (293 m)
- From the center11 miles
- Population198,722
- Jan 48° 30°
- Feb 53° 33°
- Mar 61° 40°
- Apr 71° 48°
- May 79° 57°
- Jun 86° 65°
- Jul 88° 69°
- Aug 88° 68°
- Sep 83° 61°
- Oct 72° 49°
- Nov 60° 38°
- Dec 51° 33°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Knoxville in September?
The normal high is 83°F and the normal low 61°F, for a daily mean of 71.8°F. September is 5.8°F cooler than August and 11.5°F warmer than October. September is the 4th warmest month of the year in Knoxville and the 11th wettest. Across the month the normal high falls 8°F, from 86°F on September 1 to 78°F on September 30. From one year to the next September's mean temperature typically moves about 2.7°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 69°F and 75°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 28%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 86°F | 65°F | 28% | 18% |
| September 8 | 85°F | 64°F | 26% | 17% |
| September 15 | 83°F | 62°F | 25% | 16% |
| September 22 | 81°F | 59°F | 26% | 17% |
| September 30 | 78°F | 56°F | 25% | 17% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 86°F | 65°F | 28% | 18% | 13 h |
| September 2 | 86°F | 65°F | 28% | 17% | 13 h |
| September 3 | 86°F | 65°F | 27% | 17% | 12 h 50 min |
| September 4 | 86°F | 65°F | 27% | 17% | 12 h 50 min |
| September 5 | 86°F | 64°F | 27% | 17% | 12 h 50 min |
| September 6 | 85°F | 64°F | 27% | 17% | 12 h 50 min |
| September 7 | 85°F | 64°F | 26% | 17% | 12 h 50 min |
| September 8 | 85°F | 64°F | 26% | 17% | 12 h 40 min |
| September 9 | 85°F | 63°F | 26% | 16% | 12 h 40 min |
| September 10 | 84°F | 63°F | 26% | 16% | 12 h 40 min |
| September 11 | 84°F | 63°F | 26% | 16% | 12 h 40 min |
| September 12 | 84°F | 63°F | 26% | 16% | 12 h 30 min |
| September 13 | 84°F | 62°F | 26% | 16% | 12 h 30 min |
| September 14 | 83°F | 62°F | 25% | 16% | 12 h 30 min |
| September 15 | 83°F | 62°F | 25% | 16% | 12 h 30 min |
| September 16 | 83°F | 61°F | 25% | 16% | 12 h 30 min |
| September 17 | 82°F | 61°F | 25% | 17% | 12 h 20 min |
| September 18 | 82°F | 61°F | 26% | 17% | 12 h 20 min |
| September 19 | 82°F | 60°F | 26% | 17% | 12 h 20 min |
| September 20 | 81°F | 60°F | 26% | 17% | 12 h 20 min |
| September 21 | 81°F | 59°F | 26% | 17% | 12 h 10 min |
| September 22 | 81°F | 59°F | 26% | 17% | 12 h 10 min |
| September 23 | 80°F | 59°F | 26% | 17% | 12 h 10 min |
| September 24 | 80°F | 58°F | 26% | 17% | 12 h 10 min |
| September 25 | 80°F | 58°F | 26% | 17% | 12 h 10 min |
| September 26 | 79°F | 58°F | 26% | 17% | 12 h |
| September 27 | 79°F | 57°F | 26% | 17% | 12 h |
| September 28 | 79°F | 57°F | 26% | 17% | 12 h |
| September 29 | 78°F | 56°F | 25% | 17% | 12 h |
| September 30 | 78°F | 56°F | 25% | 17% | 11 h 50 min |
- Normal high
- 83°FSeptember average
- Normal low
- 61°FSeptember average
- Precipitation
- 3.49 inmonth total
- Days with precipitation
- 80.01 inch or more
- Days at 90°F or more
- 5
- Daylight
- 13 h to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 29
- Days at 80°F or more
- 20
- Sunshine
- 76%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00013891; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Knoxville in September?
On a given September day the chance of 0.01 inch or more is 26% on average, highest around September 1 (28%). In all, 3.49 in falls on 8 days of a normal September, 1 of them with an inch or more.
In a normal September in Knoxville, 5 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00013891.
How humid and windy is Knoxville in September?
At 3 p.m. the normal temperature is 76°F with 50% relative humidity and a dew point of 56°F; at 6 a.m. it is 58°F with 91% humidity. The wind averages 4.8 mph, most often from the northwest in the afternoon.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 58°F | 55°F | 91% | 3.3 mph | 55% |
| 9 a.m. | 63°F | 57°F | 80% | 5.1 mph | 52% |
| noon | 72°F | 57°F | 58% | 6.6 mph | 54% |
| 3 p.m. | 76°F | 56°F | 50% | 7.2 mph | 49% |
| 6 p.m. | 72°F | 56°F | 56% | 5.8 mph | 57% |
| 9 p.m. | 65°F | 57°F | 74% | 3.8 mph | 62% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00013891. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for September in Knoxville?
The warmest September temperature on Knoxville's official record (since 1871) is 103°F, on September 5, 1954; the coldest is 35°F, on September 30, 1888. The wettest September brought 9.19 in (1989).
The September mean against the 1991-2020 normal of 71.8°F: 2021 70.9°F (−0.9), 2022 70.5°F (−1.3), 2023 73.3°F (+1.5), 2024 72.8°F (+1.0), 2025 72.0°F (+0.2), 2026 77.6°F (+5.8). 4 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 70.9°F | −0.9°F | 1.72 in |
| 2022 | 70.5°F | −1.3°F | 2.46 in |
| 2023 | 73.3°F | +1.5°F | 0.42 in |
| 2024 | 72.8°F | +1.0°F | 6.33 in |
| 2025 | 72.0°F | +0.2°F | 2.92 in |
| 2026 | 77.6°F | +5.8°F | 1.99 in |
Source: records: ACIS, NWS threaded record TYSthr; recent months: ACIS, station USW00013891. Records and recent months use complete months only.
How does September in Knoxville compare across Tennessee?
Across the 116 places PlainClimate covers in Tennessee, September normal highs run from 74°F in Roan Mountain to 86°F in Memphis; Knoxville's is 83°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.