Aspen weather in September

In September, Aspen sees average daytime highs of 58°F and overnight lows near 33°F, with 2.1 in of precipitation across 10.4 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 11th-wettest month of the year here.

Highs ease over the month, from about 63°F in the first days to 54°F by the end. The sky is clear or mostly clear about 45% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 54 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Aspen's 2nd-clearest and 7th-windiest month. For the whole year in context, see Aspen's year-round climate.

Daytime high: 58°; 4th warmest
Overnight low: 33°; 10th coldest
Precipitation: 2.1 in; 10.4 wet days
Daylight: 12 h 18 min; 5:54 AM – 6:09 PM
Cloud cover: 42%; 2nd clearest
Wind: 4 mph; 7th windiest
Solar energy: 5.76 kWh/m²
Travel score: 4.5; out of 10

Aspen is city in and county seat of Pitkin County, Colorado, United States.

Density: 685/km²; people per km²
Founded: 1879

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

← August Aspen 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 63°F in the first days to 54°F by the end.

A typical September day in Aspen reaches about 58°F in the afternoon and slips back to 33°F overnight — a 25°F spread between the day's warmth and the night's chill. On most days the high lands between 50°F and 66°F. Set against its neighbours, September runs about 7°F cooler than August and about 13°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)	63	63	63	62	62	62	61	61	61	60	60	60	59	59	58	58	58	57	57	57	56	56	56	55	55	55	54	54	53	53
Avg low (°F)	37	37	37	37	36	36	36	35	35	35	34	34	34	33	33	33	32	32	32	31	31	31	31	30	30	30	29	29	29	28

	Avg high (°F)	Avg low (°F)
1	63	37
2	63	37
3	63	37
4	62	37
5	62	36
6	62	36
7	61	36
8	61	35
9	61	35
10	60	35
11	60	34
12	60	34
13	59	34
14	59	33
15	58	33
16	58	33
17	58	32
18	57	32
19	57	32
20	57	31
21	56	31
22	56	31
23	56	31
24	55	30
25	55	30
26	55	30
27	54	29
28	54	29
29	53	29
30	53	28

How September really feels in Aspen

Once humidity and wind are folded in, September averages 0 days that feel above 90°F and 24 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

The story in September is cold — wind chill drags the overnight "feels like" below the raw low.

Aspen weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 11th-wettest month here — the current month is highlighted below.

Month	High / Low (°F)	Rainfall (inches)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	24° / 6°	2.3	11.3	13	9.6	0.0
Feb	27° / 8°	2.4	13.1	14	10.5	0.0
Mar	34° / 14°	2.5	12.5	13	11.7	0.0
Apr	39° / 19°	3.3	13.9	13.7	13	0.0
May	48° / 26°	2.2	11.4	7.3	14.1	1.7
Jun	60° / 32°	1.2	7.1	1.2	14.7	5.4
Jul	68° / 40°	2.3	11.7	0.1	14.5	6.2
Aug	66° / 40°	2.6	13.9	0.1	13.5	5.7
Sep	58° / 33°	2.1	10.4	2.1	12.3	4.5
Oct	45° / 21°	2.1	9.8	7.7	11	1.2
Nov	33° / 8°	2.1	9.3	10.4	9.9	0.0
Dec	24° / 3°	2.2	10.7	12.3	9.3	0.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 45% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 25% of September, with mostly cloudy or overcast conditions the remaining 31%. Skies tend to open up 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 (%)	66	66	67	67	67	67	67	67	67	67	67	68	67	68	69	69	70	71	72	73	72	73	73	73	73	72	72	72	70	70
Cloudier (%)	34	34	33	33	33	33	33	33	33	33	33	32	33	32	31	31	30	29	28	27	28	27	27	27	27	28	28	28	30	30

	Clearer (%)	Cloudier (%)
1	66	34
2	66	34
3	67	33
4	67	33
5	67	33
6	67	33
7	67	33
8	67	33
9	67	33
10	67	33
11	67	33
12	68	32
13	67	33
14	68	32
15	69	31
16	69	31
17	70	30
18	71	29
19	72	28
20	73	27
21	72	28
22	73	27
23	73	27
24	73	27
25	73	27
26	72	28
27	72	28
28	72	28
29	70	30
30	70	30

Chance of precipitation in September

Any precipitationSnow

Aspen gets around 2.1 in of rain and snow over 10.4 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 36% and peaks near 41% on the wettest days, and about 2 days bring snow. The odds ease 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 (%)	41	41	40	40	40	39	39	39	39	39	39	39	39	38	38	37	36	35	35	34	33	33	32	32	32	32	33	33	33	33
Snow chance (%)	2	2	2	2	3	3	3	3	4	4	4	5	5	6	6	7	7	8	8	9	10	10	11	12	12	13	14	15	16	16

	Rain chance (%)	Snow chance (%)
1	41	2
2	41	2
3	40	2
4	40	2
5	40	3
6	39	3
7	39	3
8	39	3
9	39	4
10	39	4
11	39	4
12	39	5
13	39	5
14	38	6
15	38	6
16	37	7
17	36	7
18	35	8
19	35	8
20	34	9
21	33	10
22	33	10
23	32	11
24	32	12
25	32	12
26	32	13
27	33	14
28	33	15
29	33	16
30	33	16

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 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.

	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)	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4
Feels	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm

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

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 min 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 78 minutes over September. Sunrise moves from 5:40 AM to 6:07 AM, and sunset from 6:34 PM to 5:46 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)	12.9	12.9	12.8	12.8	12.7	12.7	12.6	12.6	12.6	12.5	12.5	12.4	12.4	12.3	12.3	12.3	12.2	12.2	12.1	12.1	12.0	12.0	11.9	11.9	11.9	11.8	11.8	11.7	11.7	11.6
Sunrise (AM)	5:40	5:41	5:42	5:43	5:44	5:45	5:46	5:47	5:47	5:48	5:49	5:50	5:51	5:52	5:53	5:54	5:55	5:56	5:57	5:58	5:59	6:00	6:01	6:02	6:03	6:04	6:04	6:05	6:06	6:07
Sunset (PM)	6:34	6:32	6:31	6:29	6:27	6:26	6:24	6:23	6:21	6:19	6:18	6:16	6:14	6:13	6:11	6:09	6:07	6:06	6:04	6:02	6:01	5:59	5:57	5:56	5:54	5:52	5:51	5:49	5:47	5:46

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	12.9	5:40	6:34
2	12.9	5:41	6:32
3	12.8	5:42	6:31
4	12.8	5:43	6:29
5	12.7	5:44	6:27
6	12.7	5:45	6:26
7	12.6	5:46	6:24
8	12.6	5:47	6:23
9	12.6	5:47	6:21
10	12.5	5:48	6:19
11	12.5	5:49	6:18
12	12.4	5:50	6:16
13	12.4	5:51	6:14
14	12.3	5:52	6:13
15	12.3	5:53	6:11
16	12.3	5:54	6:09
17	12.2	5:55	6:07
18	12.2	5:56	6:06
19	12.1	5:57	6:04
20	12.1	5:58	6:02
21	12.0	5:59	6:01
22	12.0	6:00	5:59
23	11.9	6:01	5:57
24	11.9	6:02	5:56
25	11.9	6:03	5:54
26	11.8	6:04	5:52
27	11.8	6:04	5:51
28	11.7	6:05	5:49
29	11.7	6:06	5:47
30	11.6	6:07	5:46

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.76 kWh/m².

For context, solar energy here swings from a low near 2.54 kWh/m² to a high of 8.29 kWh/m² in June across the year — September's 5.76 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	6.2	6.1	6.1	6.1	6.0	6.0	6.0	5.9	5.9	5.8	5.8	5.8	5.8	5.7	5.7	5.7	5.6	5.6	5.5	5.5	5.5	5.4	5.4	5.3	5.3	5.2	5.2	5.1
Level	Intense	Intense	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

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

Planning a trip in September

Is September a good time to visit Aspen?

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

4.5

Sightseeing

4th-best month of the year

0.4

Beach & pool

4th-best month of the year

September is a reasonable time to visit Aspen for sightseeing.

What to pack for Aspen in September

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

In September, Aspen sees daytime highs around 58°F and nights near 33°F. Worth packing: a warm layer, rain gear and sun protection. About 10 days see rain.

a warm layerrain gearsun protection

UV index in Aspen in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Aspen peaks around June 22 at about 12 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near January 10 at about 3 (moderate).

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

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	3	4	7	7	10	13	12	11	8	6	4	3
Level	Moderate	Moderate	High	Very high	Very high	Extreme	Extreme	Extreme	Very high	High	Moderate	Moderate

	UV index (midday)	Level
Jan	3	Moderate
Feb	4	Moderate
Mar	7	High
Apr	7	Very high
May	10	Very high
Jun	13	Extreme
Jul	12	Extreme
Aug	11	Extreme
Sep	8	Very high
Oct	6	High
Nov	4	Moderate
Dec	3	Moderate

Location & terrain

Where is Aspen?

Aspen sits at 39.2°N, 106.8°W, 0 ft above sea level, in United States. The nearest listed city is Montrose, 75 mi away.

Topography around Aspen

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

Within 2 miles, the terrain around Aspen has large variations in elevation — a maximum elevation change of 2,887 ft around an average of 8,688 ft above sea level; within 10 miles, very significant variations in elevation — a maximum elevation change of 6,417 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 8,927 ft.

The land around Aspen is covered by trees (77%) within 2 miles, trees (74%) within 10 miles, and trees (64%) and grassland (24%) within 50 miles.

2 miles

2,887 ft

trees 77%

10 miles

6,417 ft

trees 74%

50 miles

8,927 ft

trees 64%

treesgrasslandartificial surfacesbare terrainmoss and lichen

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

September weather nearby: Montrose 75 mi · Clifton 88 mi · Grand Junction 93 mi · Golden 94 mi · Dakota Ridge 94 mi · Ken Caryl 95 mi · Columbine 98 mi · Lakewood 99 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 Aspen (39.1911°, -106.8175°, elevation 0 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	63	37
2	63	37
3	63	37
4	62	37
5	62	36
6	62	36
7	61	36
8	61	35
9	61	35
10	60	35
11	60	34
12	60	34
13	59	34
14	59	33
15	58	33
16	58	33
17	58	32
18	57	32
19	57	32
20	57	31
21	56	31
22	56	31
23	56	31
24	55	30
25	55	30
26	55	30
27	54	29
28	54	29
29	53	29
30	53	28

	Clearer (%)	Cloudier (%)
1	66	34
2	66	34
3	67	33
4	67	33
5	67	33
6	67	33
7	67	33
8	67	33
9	67	33
10	67	33
11	67	33
12	68	32
13	67	33
14	68	32
15	69	31
16	69	31
17	70	30
18	71	29
19	72	28
20	73	27
21	72	28
22	73	27
23	73	27
24	73	27
25	73	27
26	72	28
27	72	28
28	72	28
29	70	30
30	70	30

	Rain chance (%)	Snow chance (%)
1	41	2
2	41	2
3	40	2
4	40	2
5	40	3
6	39	3
7	39	3
8	39	3
9	39	4
10	39	4
11	39	4
12	39	5
13	39	5
14	38	6
15	38	6
16	37	7
17	36	7
18	35	8
19	35	8
20	34	9
21	33	10
22	33	10
23	32	11
24	32	12
25	32	12
26	32	13
27	33	14
28	33	15
29	33	16
30	33	16

	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	63	37
2	63	37
3	63	37
4	62	37
5	62	36
6	62	36
7	61	36
8	61	35
9	61	35
10	60	35
11	60	34
12	60	34
13	59	34
14	59	33
15	58	33
16	58	33
17	58	32
18	57	32
19	57	32
20	57	31
21	56	31
22	56	31
23	56	31
24	55	30
25	55	30
26	55	30
27	54	29
28	54	29
29	53	29
30	53	28

	Clearer (%)	Cloudier (%)
1	66	34
2	66	34
3	67	33
4	67	33
5	67	33
6	67	33
7	67	33
8	67	33
9	67	33
10	67	33
11	67	33
12	68	32
13	67	33
14	68	32
15	69	31
16	69	31
17	70	30
18	71	29
19	72	28
20	73	27
21	72	28
22	73	27
23	73	27
24	73	27
25	73	27
26	72	28
27	72	28
28	72	28
29	70	30
30	70	30

	Rain chance (%)	Snow chance (%)
1	41	2
2	41	2
3	40	2
4	40	2
5	40	3
6	39	3
7	39	3
8	39	3
9	39	4
10	39	4
11	39	4
12	39	5
13	39	5
14	38	6
15	38	6
16	37	7
17	36	7
18	35	8
19	35	8
20	34	9
21	33	10
22	33	10
23	32	11
24	32	12
25	32	12
26	32	13
27	33	14
28	33	15
29	33	16
30	33	16

	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	63	37
2	63	37
3	63	37
4	62	37
5	62	36
6	62	36
7	61	36
8	61	35
9	61	35
10	60	35
11	60	34
12	60	34
13	59	34
14	59	33
15	58	33
16	58	33
17	58	32
18	57	32
19	57	32
20	57	31
21	56	31
22	56	31
23	56	31
24	55	30
25	55	30
26	55	30
27	54	29
28	54	29
29	53	29
30	53	28

	Clearer (%)	Cloudier (%)
1	66	34
2	66	34
3	67	33
4	67	33
5	67	33
6	67	33
7	67	33
8	67	33
9	67	33
10	67	33
11	67	33
12	68	32
13	67	33
14	68	32
15	69	31
16	69	31
17	70	30
18	71	29
19	72	28
20	73	27
21	72	28
22	73	27
23	73	27
24	73	27
25	73	27
26	72	28
27	72	28
28	72	28
29	70	30
30	70	30

	Rain chance (%)	Snow chance (%)
1	41	2
2	41	2
3	40	2
4	40	2
5	40	3
6	39	3
7	39	3
8	39	3
9	39	4
10	39	4
11	39	4
12	39	5
13	39	5
14	38	6
15	38	6
16	37	7
17	36	7
18	35	8
19	35	8
20	34	9
21	33	10
22	33	10
23	32	11
24	32	12
25	32	12
26	32	13
27	33	14
28	33	15
29	33	16
30	33	16

	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