Casper weather in September

In September, Casper sees average daytime highs of 71°F and overnight lows near 46°F, with 1.1 in of precipitation across 5.6 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 6th-wettest month of the year here.

Highs ease over the month, from about 78°F in the first days to 65°F by the end. The sky is clear or mostly clear about 58% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Casper's 1st-clearest and 10th-windiest month. For the whole year in context, see Casper's year-round climate.

Daytime high: 71°; 4th warmest
Overnight low: 46°; 9th coldest
Precipitation: 1.1 in; 5.6 wet days
Daylight: 12 h 18 min; 5:51 AM – 6:08 PM
Cloud cover: 38%; 1st clearest
Wind: 8 mph; 10th windiest
Solar energy: 5.43 kWh/m²
Travel score: 7.5; out of 10

Casper is city in and county seat of Natrona County, Wyoming, United States.

Density: 868/km²; people per km²

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

← August Casper year-round climate October →Best places to visit in September

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 78°F in the first days to 65°F by the end.

A typical September day in Casper reaches about 71°F in the afternoon and slips back to 46°F overnight — a 25°F spread between the day's warmth and the night's chill. On most days the high lands between 56°F and 83°F. Set against its neighbours, September runs about 11°F cooler than August and about 16°F warmer than October.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Avg high (°F)	78	78	78	77	76	76	75	75	74	74	73	73	72	71	71	70	70	69	69	68	68	67	67	66	66	65	65	65	64	64
Avg low (°F)	52	51	51	51	50	50	49	49	48	48	47	47	47	46	46	45	45	44	44	44	43	43	42	42	42	41	41	41	40	40

	Avg high (°F)	Avg low (°F)
1	78	52
2	78	51
3	78	51
4	77	51
5	76	50
6	76	50
7	75	49
8	75	49
9	74	48
10	74	48
11	73	47
12	73	47
13	72	47
14	71	46
15	71	46
16	70	45
17	70	45
18	69	44
19	69	44
20	68	44
21	68	43
22	67	43
23	67	42
24	66	42
25	66	42
26	65	41
27	65	41
28	65	41
29	64	40
30	64	40

How September really feels in Casper

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

heat index over the day's high

Days feeling ≤ 32°F

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.

Casper weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 6th-wettest month here — the current month is highlighted below.

Month	High / Low (°F)	Rainfall (inches)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	29° / 12°	0.8	5.6	5.7	9.2	0.0
Feb	32° / 13°	1.0	5.9	5.8	10.2	0.0
Mar	42° / 22°	1.5	7.1	6	11.6	0.5
Apr	50° / 29°	2.3	10.8	7	13.1	2.3
May	62° / 39°	2.7	11.1	2.3	14.4	5.0
Jun	75° / 49°	1.4	6.3	0.1	15.1	7.5
Jul	84° / 56°	0.7	4.5	0	14.8	6.5
Aug	82° / 55°	0.6	4.1	0	13.8	7.3
Sep	71° / 46°	1.1	5.6	0.7	12.3	7.5
Oct	55° / 33°	1.8	7	4.1	10.8	4.0
Nov	41° / 22°	1.1	5.7	5.5	9.5	0.4
Dec	30° / 13°	0.9	5.6	6.1	8.9	0.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 58% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 28%. Skies tend to cloud over as the month goes on.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Clearer (%)	77	77	76	76	76	74	74	74	73	73	72	72	72	71	70	70	70	71	71	71	71	71	71	71	71	70	70	70	70	70
Cloudier (%)	23	23	24	24	24	26	26	26	27	27	28	28	28	29	30	30	30	29	29	29	29	29	29	29	29	30	30	30	30	30

	Clearer (%)	Cloudier (%)
1	77	23
2	77	23
3	76	24
4	76	24
5	76	24
6	74	26
7	74	26
8	74	26
9	73	27
10	73	27
11	72	28
12	72	28
13	72	28
14	71	29
15	70	30
16	70	30
17	70	30
18	71	29
19	71	29
20	71	29
21	71	29
22	71	29
23	71	29
24	71	29
25	71	29
26	70	30
27	70	30
28	70	30
29	70	30
30	70	30

Chance of precipitation in September

Any precipitationSnow

Casper gets around 1.1 in of rain and snow over 5.6 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 19% and peaks near 22% on the wettest days, and about 1 day brings snow. The odds climb toward the end of the month.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Rain chance (%)	14	14	15	16	17	17	18	18	19	19	19	20	20	20	20	20	20	20	20	19	19	20	20	20	21	21	21	22	22	22
Snow chance (%)	0	1	1	1	1	1	1	1	1	1	1	2	2	2	2	2	3	3	3	3	3	4	4	4	5	5	6	7	7	8

	Rain chance (%)	Snow chance (%)
1	14	0
2	14	1
3	15	1
4	16	1
5	17	1
6	17	1
7	18	1
8	18	1
9	19	1
10	19	1
11	19	1
12	20	2
13	20	2
14	20	2
15	20	2
16	20	2
17	20	3
18	20	3
19	20	3
20	19	3
21	19	3
22	20	4
23	20	4
24	20	4
25	21	5
26	21	5
27	21	6
28	22	7
29	22	7
30	22	8

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Dry (%)	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

Wind in September

Winds average 8 mph in September.

Across September, daily wind ranges from about 7 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Wind speed (mph)	7	7	7	7	7	7	7	7	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8
Feels	calm	calm	calm	calm	calm	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze

	Wind speed (mph)	Feels
1	7	calm
2	7	calm
3	7	calm
4	7	calm
5	7	calm
6	7	light breeze
7	7	light breeze
8	7	light breeze
9	8	light breeze
10	8	light breeze
11	8	light breeze
12	8	light breeze
13	8	light breeze
14	8	light breeze
15	8	light breeze
16	8	light breeze
17	8	light breeze
18	8	light breeze
19	8	light breeze
20	8	light breeze
21	8	light breeze
22	8	light breeze
23	8	light breeze
24	8	light breeze
25	8	light breeze
26	8	light breeze
27	8	light breeze
28	8	light breeze
29	8	light breeze
30	8	light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 84 minutes over September. Sunrise moves from 5:34 AM to 6:07 AM, and sunset from 6:36 PM to 5:42 PM.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Daylight (h)	13.0	13.0	12.9	12.9	12.8	12.8	12.7	12.7	12.6	12.6	12.5	12.5	12.4	12.4	12.3	12.3	12.2	12.2	12.1	12.1	12.0	12.0	11.9	11.9	11.8	11.8	11.7	11.7	11.6	11.6
Sunrise (AM)	5:34	5:35	5:36	5:38	5:39	5:40	5:41	5:42	5:43	5:44	5:45	5:46	5:48	5:49	5:50	5:51	5:52	5:53	5:54	5:55	5:57	5:58	5:59	6:00	6:01	6:02	6:03	6:05	6:06	6:07
Sunset (PM)	6:36	6:34	6:32	6:30	6:29	6:27	6:25	6:23	6:21	6:19	6:17	6:16	6:14	6:12	6:10	6:08	6:06	6:04	6:03	6:01	5:59	5:57	5:55	5:53	5:51	5:50	5:48	5:46	5:44	5:42

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	13.0	5:34	6:36
2	13.0	5:35	6:34
3	12.9	5:36	6:32
4	12.9	5:38	6:30
5	12.8	5:39	6:29
6	12.8	5:40	6:27
7	12.7	5:41	6:25
8	12.7	5:42	6:23
9	12.6	5:43	6:21
10	12.6	5:44	6:19
11	12.5	5:45	6:17
12	12.5	5:46	6:16
13	12.4	5:48	6:14
14	12.4	5:49	6:12
15	12.3	5:50	6:10
16	12.3	5:51	6:08
17	12.2	5:52	6:06
18	12.2	5:53	6:04
19	12.1	5:54	6:03
20	12.1	5:55	6:01
21	12.0	5:57	5:59
22	12.0	5:58	5:57
23	11.9	5:59	5:55
24	11.9	6:00	5:53
25	11.8	6:01	5:51
26	11.8	6:02	5:50
27	11.7	6:03	5:48
28	11.7	6:05	5:46
29	11.6	6:06	5:44
30	11.6	6:07	5:42

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.43 kWh/m².

For context, solar energy here swings from a low near 2.16 kWh/m² to a high of 7.76 kWh/m² in June across the year — September's 5.43 kWh/m² falls in the middle.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Solar energy (kWh/m²)	6.2	6.2	6.1	6.1	6.0	6.0	5.9	5.8	5.8	5.7	5.7	5.6	5.5	5.5	5.4	5.4	5.3	5.3	5.2	5.2	5.1	5.0	5.0	4.9	4.9	4.8	4.8	4.7	4.7	4.6
Level	Intense	Intense	Intense	Intense	Intense	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright

	Solar energy (kWh/m²)	Level
1	6.2	Intense
2	6.2	Intense
3	6.1	Intense
4	6.1	Intense
5	6.0	Intense
6	6.0	Bright
7	5.9	Bright
8	5.8	Bright
9	5.8	Bright
10	5.7	Bright
11	5.7	Bright
12	5.6	Bright
13	5.5	Bright
14	5.5	Bright
15	5.4	Bright
16	5.4	Bright
17	5.3	Bright
18	5.3	Bright
19	5.2	Bright
20	5.2	Bright
21	5.1	Bright
22	5.0	Bright
23	5.0	Bright
24	4.9	Bright
25	4.9	Bright
26	4.8	Bright
27	4.8	Bright
28	4.7	Bright
29	4.7	Bright
30	4.6	Bright

Planning a trip in September

Is September a good time to visit Casper?

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

7.5

Sightseeing

1st-best month of the year

4.9

Beach & pool

4th-best month of the year

September is one of the better times to visit Casper for general sightseeing.

What to pack for Casper in September

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

In September, Casper sees daytime highs around 71°F and nights near 46°F. Worth packing: a warm layer and sun protection. About 6 days see rain.

a warm layersun protection

UV index in Casper 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 Casper peaks around July 11 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	2	3	5	6	8	10	10	8	7	4	3	2
Level	Low	Moderate	High	High	Very high	Very high	Very high	Very high	High	Moderate	Moderate	Low

	UV index (midday)	Level
Jan	2	Low
Feb	3	Moderate
Mar	5	High
Apr	6	High
May	8	Very high
Jun	10	Very high
Jul	10	Very high
Aug	8	Very high
Sep	7	High
Oct	4	Moderate
Nov	3	Moderate
Dec	2	Low

Location & terrain

Where is Casper?

Casper sits at 42.9°N, 106.3°W, 5,118 ft above sea level, in United States. The nearest listed city is Gillette, 106 mi away.

Topography around Casper

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

Within 2 miles, the terrain around Casper has only modest variations in elevation — a maximum elevation change of 282 ft around an average of 5,180 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,173 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,770 ft.

The land around Casper is covered by grassland (49%) and artificial surfaces (32%) within 2 miles, grassland (81%) within 10 miles, and grassland (91%) within 50 miles.

2 miles

282 ft

grassland 49%

10 miles

3,173 ft

grassland 81%

50 miles

4,770 ft

grassland 91%

treesshrubsgrasslandcroplandartificial surfacesbare terrainwater

← August Casper year-round climate October →Best places to visit in September

September weather nearby: Gillette 106 mi · Laramie 114 mi · Sheridan 137 mi · Cheyenne 142 mi · Fort Collins 170 mi · Rock Springs 172 mi · Rapid City 176 mi · Estes Park 177 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

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 Casper (42.8666°, -106.3131°, elevation 5,118 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. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).

	Avg high (°F)	Avg low (°F)
1	78	52
2	78	51
3	78	51
4	77	51
5	76	50
6	76	50
7	75	49
8	75	49
9	74	48
10	74	48
11	73	47
12	73	47
13	72	47
14	71	46
15	71	46
16	70	45
17	70	45
18	69	44
19	69	44
20	68	44
21	68	43
22	67	43
23	67	42
24	66	42
25	66	42
26	65	41
27	65	41
28	65	41
29	64	40
30	64	40

	Clearer (%)	Cloudier (%)
1	77	23
2	77	23
3	76	24
4	76	24
5	76	24
6	74	26
7	74	26
8	74	26
9	73	27
10	73	27
11	72	28
12	72	28
13	72	28
14	71	29
15	70	30
16	70	30
17	70	30
18	71	29
19	71	29
20	71	29
21	71	29
22	71	29
23	71	29
24	71	29
25	71	29
26	70	30
27	70	30
28	70	30
29	70	30
30	70	30

	Rain chance (%)	Snow chance (%)
1	14	0
2	14	1
3	15	1
4	16	1
5	17	1
6	17	1
7	18	1
8	18	1
9	19	1
10	19	1
11	19	1
12	20	2
13	20	2
14	20	2
15	20	2
16	20	2
17	20	3
18	20	3
19	20	3
20	19	3
21	19	3
22	20	4
23	20	4
24	20	4
25	21	5
26	21	5
27	21	6
28	22	7
29	22	7
30	22	8

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

	Avg high (°F)	Avg low (°F)
1	78	52
2	78	51
3	78	51
4	77	51
5	76	50
6	76	50
7	75	49
8	75	49
9	74	48
10	74	48
11	73	47
12	73	47
13	72	47
14	71	46
15	71	46
16	70	45
17	70	45
18	69	44
19	69	44
20	68	44
21	68	43
22	67	43
23	67	42
24	66	42
25	66	42
26	65	41
27	65	41
28	65	41
29	64	40
30	64	40

	Clearer (%)	Cloudier (%)
1	77	23
2	77	23
3	76	24
4	76	24
5	76	24
6	74	26
7	74	26
8	74	26
9	73	27
10	73	27
11	72	28
12	72	28
13	72	28
14	71	29
15	70	30
16	70	30
17	70	30
18	71	29
19	71	29
20	71	29
21	71	29
22	71	29
23	71	29
24	71	29
25	71	29
26	70	30
27	70	30
28	70	30
29	70	30
30	70	30

	Rain chance (%)	Snow chance (%)
1	14	0
2	14	1
3	15	1
4	16	1
5	17	1
6	17	1
7	18	1
8	18	1
9	19	1
10	19	1
11	19	1
12	20	2
13	20	2
14	20	2
15	20	2
16	20	2
17	20	3
18	20	3
19	20	3
20	19	3
21	19	3
22	20	4
23	20	4
24	20	4
25	21	5
26	21	5
27	21	6
28	22	7
29	22	7
30	22	8

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

	Avg high (°F)	Avg low (°F)
1	78	52
2	78	51
3	78	51
4	77	51
5	76	50
6	76	50
7	75	49
8	75	49
9	74	48
10	74	48
11	73	47
12	73	47
13	72	47
14	71	46
15	71	46
16	70	45
17	70	45
18	69	44
19	69	44
20	68	44
21	68	43
22	67	43
23	67	42
24	66	42
25	66	42
26	65	41
27	65	41
28	65	41
29	64	40
30	64	40

	Clearer (%)	Cloudier (%)
1	77	23
2	77	23
3	76	24
4	76	24
5	76	24
6	74	26
7	74	26
8	74	26
9	73	27
10	73	27
11	72	28
12	72	28
13	72	28
14	71	29
15	70	30
16	70	30
17	70	30
18	71	29
19	71	29
20	71	29
21	71	29
22	71	29
23	71	29
24	71	29
25	71	29
26	70	30
27	70	30
28	70	30
29	70	30
30	70	30

	Rain chance (%)	Snow chance (%)
1	14	0
2	14	1
3	15	1
4	16	1
5	17	1
6	17	1
7	18	1
8	18	1
9	19	1
10	19	1
11	19	1
12	20	2
13	20	2
14	20	2
15	20	2
16	20	2
17	20	3
18	20	3
19	20	3
20	19	3
21	19	3
22	20	4
23	20	4
24	20	4
25	21	5
26	21	5
27	21	6
28	22	7
29	22	7
30	22	8

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100