Knoxville weather in September

In September, Knoxville sees average daytime highs of 81°F and overnight lows near 62°F, with 3.5 in of rain across 8.3 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 10th-wettest month of the year here.

Highs ease over the month, from about 84°F in the first days to 77°F by the end. The sky is clear or mostly clear about 43% of the time in September, and the air most often feels humid.

Daylight stretches from about 12 h 48 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is Knoxville's 2nd-clearest and 10th-windiest month. For the whole year in context, see Knoxville's year-round climate.

Daytime high
81°
4th warmest
Overnight low
62°
9th coldest
Rainfall
3.5 in
8.3 wet days
Daylight
12 h 12 min
6:23 AM – 6:37 PM
Cloud cover
50%
2nd clearest
Wind
4 mph
10th windiest
Solar energy
4.6 kWh/m²
Travel score
6.7
out of 10

Knoxville is city and county seat of Knox County, State of Tennessee, United States.

Density
707/km²
people per km²
Founded
1786

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 84°F in the first days to 77°F by the end.

A typical September day in Knoxville reaches about 81°F in the afternoon and slips back to 62°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 72°F and 89°F. Set against its neighbours, September runs about 5°F cooler than August and about 11°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18566
28566
38466
48466
58465
68465
78365
88364
98364
108364
118264
128263
138263
148263
158162
168162
178162
188061
198061
208060
217960
227960
237859
247859
257858
267758
277758
287757
297657
307656

How September really feels in Knoxville

Once humidity and wind are folded in, September averages 0 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Knoxville weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan47° / 31°4.410.71.89.81.6
Feb52° / 34°4.310.91.710.62.6
Mar60° / 41°4.912.20.711.74.6
Apr69° / 49°4.310.9012.96.2
May77° / 58°3.711.7013.96.5
Jun84° / 66°3.713.2014.45.2
Jul86° / 70°4.714.8014.24.4
Aug86° / 68°3.411.4013.44.9
Sep81° / 62°3.58.3012.26.7
Oct70° / 50°2.97.8011.17.0
Nov59° / 40°3.88.90.210.14.7
Dec50° / 35°4.610.619.62.3

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 43% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 40%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16040
26040
36139
46139
56139
66139
76139
86139
96139
106040
116139
126040
136040
146040
155941
165842
175743
185842
195743
205743
215842
225842
235842
246040
256040
266139
276238
286337
296337
306436

Chance of precipitation in September

Any precipitation

Knoxville gets around 3.5 in of rain over 8.3 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 27% and peaks near 29% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
129
228
328
428
527
627
727
827
926
1026
1126
1226
1325
1426
1526
1626
1727
1827
1927
2028
2128
2228
2328
2427
2527
2627
2726
2826
2926
3026

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the humid band about 29% of days. Sticky, muggy-or-worse air turns up on roughly 31% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1411235111
2512234910
3613244710
461425459
571526438
681727417
791828397
8101928376
9112029355
10122129335
11132230324
12142230304
13152330293
14162430283
15162431263
16172431252
17182531242
18192532222
19202532212
20222432202
21232432192
22252432181
23272431171
24292430161
25312429151
26332328141
27352327131
28372326121
29392325111
30412424101

Wind in September

Winds average 4 mph in September.

Across September, daily wind ranges from about 4 mph on the calmest days to 4 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 48 min at the start of September to 11 h 42 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 66 minutes over September. Sunrise moves from 6:11 AM to 6:35 AM, and sunset from 6:59 PM to 6:15 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.86:116:59
212.86:126:58
312.76:136:56
412.76:146:55
512.66:156:53
612.66:156:52
712.66:166:50
812.56:176:49
912.56:186:47
1012.56:196:46
1112.46:196:44
1212.46:206:43
1312.36:216:41
1412.36:226:40
1512.36:226:38
1612.26:236:37
1712.26:246:35
1812.16:256:34
1912.16:266:32
2012.16:266:31
2112.06:276:29
2212.06:286:27
2312.06:296:26
2411.96:306:24
2511.96:316:23
2611.86:316:21
2711.86:326:20
2811.86:336:18
2911.76:346:17
3011.76:356:15

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.6 kWh/m².

For context, solar energy here swings from a low near 2.07 kWh/m² to a high of 6.07 kWh/m² in June across the year — September's 4.6 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.1Bright
25.1Bright
35.1Bright
45.0Bright
55.0Bright
65.0Bright
75.0Bright
84.9Bright
94.9Bright
104.8Bright
114.8Bright
124.8Bright
134.7Bright
144.7Bright
154.6Bright
164.6Bright
174.6Bright
184.5Bright
194.5Bright
204.4Bright
214.4Bright
224.4Bright
234.3Bright
244.3Bright
254.3Bright
264.3Bright
274.3Bright
284.2Bright
294.2Bright
304.2Bright
Planning a trip in September

Is September a good time to visit Knoxville?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

6.7
Sightseeing
2nd-best month of the year
7.0
Beach & pool
1st-best month of the year

September is a reasonable time to visit Knoxville for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Knoxville in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Knoxville sees daytime highs around 81°F and nights near 62°F. Pack light clothes. Worth having: rain gear and sun protection. About 8 days see rain.

light clothesrain gearsun protection

UV index in Knoxville in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Knoxville peaks around July 12 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJul 12UV 10Dec 19UV 2
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar6High
Apr7High
May8Very high
Jun9Very high
Jul10Very high
Aug8Very high
Sep7High
Oct5Moderate
Nov4Moderate
Dec2Moderate

Air quality in Knoxville in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Knoxville is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.8× the cleanest month (December, 7 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1518 µg/m³Dec 237 µg/m³
PM2.5 (µg/m³)Level
Jan7Good
Feb8Good
Mar11Good
Apr11Good
May13Moderate
Jun16Moderate
Jul18Moderate
Aug15Moderate
Sep11Good
Oct8Good
Nov9Good
Dec7Good
Location & terrain

Where is Knoxville?

Knoxville sits at 36.0°N, 83.9°W, 906 ft above sea level, in United States. The nearest listed city is Farragut, 14 mi away.

Topography around Knoxville

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Knoxville.

Within 2 miles, the terrain around Knoxville has only modest variations in elevation — a maximum elevation change of 390 ft around an average of 919 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 879 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 5,974 ft.

The land around Knoxville is covered by artificial surfaces (45%) and trees (39%) within 2 miles, trees (65%) and grassland (21%) within 10 miles, and trees (79%) within 50 miles.

2 miles
390 ft
10 miles
879 ft
50 miles
5,974 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Farragut 14 mi · Maryville 14 mi · Oak Ridge 20 mi · Sevierville 21 mi · Gatlinburg 29 mi · Morristown 39 mi · Greeneville 63 mi · Cleveland 77 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Knoxville (35.9606°, -83.9207°, elevation 906 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).