Stillwater weather in September

In September, Stillwater sees average daytime highs of 83°F and overnight lows near 64°F, with 3.1 in of rain across 7.3 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 88°F in the first days to 79°F by the end. The sky is clear or mostly clear about 55% of the time in September, and the air most often feels muggy.

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 Stillwater's 2nd-clearest and 10th-windiest month. For the whole year in context, see Stillwater's year-round climate.

Daytime high
83°
4th warmest
Overnight low
64°
9th coldest
Rainfall
3.1 in
7.3 wet days
Daylight
12 h 12 min
6:16 AM – 6:29 PM
Cloud cover
40%
2nd clearest
Wind
7 mph
10th windiest
Solar energy
5.04 kWh/m²
Travel score
6.3
out of 10

Stillwater is city in Oklahoma, United States.

Density
630/km²
people per km²
Founded
1884

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 88°F in the first days to 79°F by the end.

A typical September day in Stillwater reaches about 83°F in the afternoon and slips back to 64°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 74°F and 93°F. Set against its neighbours, September runs about 8°F cooler than August and about 11°F warmer than October.

40°60°80°100°151015202530
Avg high (°F)Avg low (°F)
18969
28969
38869
48868
58768
68767
78767
88667
98666
108566
118566
128565
138465
148465
158364
168364
178363
188263
198263
208262
218262
228161
238161
248160
258060
268060
278059
287959
297958
307958

How September really feels in Stillwater

Once humidity and wind are folded in, September averages 2 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
2
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Stillwater weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan48° / 30°1.55.31.39.82.1
Feb53° / 33°1.85.71.310.63.4
Mar62° / 42°2.98.10.711.75.6
Apr71° / 50°4.19012.96.8
May79° / 60°4.811.2013.96.5
Jun88° / 69°4.19.9014.44.6
Jul93° / 73°2.97.4014.23.5
Aug91° / 72°2.66.9013.43.9
Sep83° / 64°3.17.3012.26.3
Oct72° / 52°3.27.60.111.17.4
Nov60° / 41°2.05.70.410.15.5
Dec50° / 32°1.85.41.39.62.5

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 55% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 31%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17327
27327
37228
47129
57030
66832
76832
86733
96634
106634
116535
126535
136535
146535
156436
166436
176436
186535
196634
206733
216832
227030
237129
247129
257327
267426
277426
287426
297525
307525

Chance of precipitation in September

Any precipitation

Stillwater gets around 3.1 in of rain over 7.3 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 25% and peaks near 27% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
123
224
324
424
525
625
725
826
926
1026
1127
1227
1327
1427
1527
1627
1727
1827
1926
2025
2125
2224
2323
2423
2522
2622
2721
2821
2921
3021

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the muggy band about 29% of days. Sticky, muggy-or-worse air turns up on roughly 36% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1712264312
2812274112
3913274011
41014273811
51114273711
61314273610
71415263510
8151526359
9161525349
10171524349
11191524348
12201623348
13211622338
14221622337
15231721327
16251721317
17261720306
18281720296
19301719286
20321719276
21341718256
22361718235
23381718225
24411717205
25431717195
26451716174
27471716164
28491715154
29511715143
30521814133

Wind in September

Winds average 7 mph in September.

Across September, daily wind ranges from about 7 mph on the calmest days to 7 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297light breeze
307light breeze

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 6:04 AM to 6:27 AM, and sunset from 6:52 PM to 6:08 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.86:046:52
212.86:056:51
312.76:056:49
412.76:066:48
512.76:076:46
612.66:086:45
712.66:096:43
812.56:096:42
912.56:106:40
1012.56:116:39
1112.46:126:37
1212.46:136:35
1312.36:136:34
1412.36:146:32
1512.36:156:31
1612.26:166:29
1712.26:176:28
1812.16:176:26
1912.16:186:25
2012.16:196:23
2112.06:206:22
2212.06:216:20
2312.06:216:19
2411.96:226:17
2511.96:236:15
2611.86:246:14
2711.86:256:12
2811.86:266:11
2911.76:266:09
3011.76:276:08

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.04 kWh/m².

For context, solar energy here swings from a low near 2.4 kWh/m² to a high of 6.84 kWh/m² in July across the year — September's 5.04 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.6Bright
25.6Bright
35.5Bright
45.5Bright
55.4Bright
65.4Bright
75.3Bright
85.3Bright
95.2Bright
105.2Bright
115.1Bright
125.1Bright
135.0Bright
145.0Bright
155.0Bright
164.9Bright
174.9Bright
184.9Bright
194.9Bright
204.8Bright
214.8Bright
224.8Bright
234.8Bright
244.8Bright
254.8Bright
264.8Bright
274.8Bright
284.7Bright
294.7Bright
304.7Bright
Planning a trip in September

Is September a good time to visit Stillwater?

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

6.3
Sightseeing
4th-best month of the year
7.4
Beach & pool
1st-best month of the year

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

What to pack for Stillwater in September

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

In September, Stillwater sees daytime highs around 83°F and nights near 64°F. Pack light clothes. Worth having: sun protection. About 7 days see rain.

light clothessun protection

UV index in Stillwater 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 Stillwater peaks around July 12 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateVery highHighModerateJul 12UV 10Dec 21UV 2
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar5High
Apr9Very high
May8Very high
Jun10Very high
Jul10Very high
Aug10Very high
Sep7Very high
Oct5High
Nov4Moderate
Dec2Moderate

Air quality in Stillwater 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 Stillwater is worst in July — around 15 µg/m³ PM2.5 (moderate), about 3.3× the cleanest month (November, 5 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodJul 1815 µg/m³Nov 165 µg/m³
PM2.5 (µg/m³)Level
Jan6Good
Feb8Good
Mar12Good
Apr13Moderate
May11Good
Jun12Moderate
Jul15Moderate
Aug13Moderate
Sep9Good
Oct5Good
Nov5Good
Dec5Good
Location & terrain

Where is Stillwater?

Stillwater sits at 36.1°N, 97.1°W, 896 ft above sea level, in United States. The nearest listed city is Edmond, 40 mi away.

Topography around Stillwater

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

Within 2 miles, the terrain around Stillwater has only modest variations in elevation — a maximum elevation change of 138 ft around an average of 902 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 341 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 719 ft.

The land around Stillwater is covered by trees (35%), artificial surfaces (33%) and grassland (24%) within 2 miles, grassland (50%) and trees (39%) within 10 miles, and grassland (47%) and trees (32%) within 50 miles.

2 miles
138 ft
10 miles
341 ft
50 miles
719 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Edmond 40 mi · Ponca City 41 mi · Enid 50 mi · Midwest City 50 mi · Del City 51 mi · Oklahoma City 52 mi · Bethany 52 mi · Sand Springs 53 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 Stillwater (36.1156°, -97.0584°, elevation 896 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).