Castle Rock weather in September

In September, Castle Rock sees average daytime highs of 72°F and overnight lows near 45°F, with 1.3 in of precipitation across 6.4 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 8th-wettest month of the year here.

Highs ease over the month, from about 76°F in the first days to 68°F by the end. The sky is clear or mostly clear about 54% 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 Castle Rock's 4th-clearest and 9th-windiest month. For the whole year in context, see Castle Rock's year-round climate.

Daytime high: 72°; 4th warmest
Overnight low: 45°; 9th coldest
Precipitation: 1.3 in; 6.4 wet days
Daylight: 12 h 18 min; 5:46 AM – 6:01 PM
Cloud cover: 39%; 4th clearest
Wind: 5 mph; 9th windiest
Solar energy: 5.54 kWh/m²
Travel score: 7.6; out of 10

Castle Rock is town in and seat of Douglas County, Colorado, United States.

Density: 635/km²; people per km²
Founded: 1874

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

← August Castle Rock 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 76°F in the first days to 68°F by the end.

A typical September day in Castle Rock reaches about 72°F in the afternoon and slips back to 45°F overnight — a 28°F spread between the day's warmth and the night's chill. On most days the high lands between 61°F and 82°F. Set against its neighbours, September runs about 7°F cooler than August and about 12°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)	77	77	76	76	76	75	75	75	74	74	74	74	73	73	73	72	72	72	71	71	71	70	70	70	69	69	69	68	68	68
Avg low (°F)	50	50	49	49	49	48	48	47	47	47	46	46	46	45	45	45	44	44	43	43	43	42	42	42	41	41	40	40	40	39

	Avg high (°F)	Avg low (°F)
1	77	50
2	77	50
3	76	49
4	76	49
5	76	49
6	75	48
7	75	48
8	75	47
9	74	47
10	74	47
11	74	46
12	74	46
13	73	46
14	73	45
15	73	45
16	72	45
17	72	44
18	72	44
19	71	43
20	71	43
21	71	43
22	70	42
23	70	42
24	70	42
25	69	41
26	69	41
27	69	40
28	68	40
29	68	40
30	68	39

How September really feels in Castle Rock

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.

Castle Rock weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 8th-wettest month here — the current month is highlighted below.

Month	High / Low (°F)	Rainfall (inches)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	39° / 12°	0.6	4.2	4.7	9.5	0.0
Feb	42° / 15°	0.7	5	5.4	10.5	0.3
Mar	49° / 22°	1.7	6.9	5.9	11.7	2.2
Apr	55° / 28°	2.6	9.7	6.1	13	3.5
May	65° / 39°	3.0	12.3	1.7	14.1	5.5
Jun	76° / 48°	2.1	10.2	0.1	14.7	6.8
Jul	81° / 54°	2.5	10.9	0	14.5	6.5
Aug	79° / 52°	2.0	10.1	0	13.5	6.9
Sep	72° / 45°	1.3	6.4	0.5	12.3	7.6
Oct	60° / 32°	1.4	5.5	2.4	11	5.7
Nov	48° / 21°	1.0	4.9	4.9	9.8	2.0
Dec	39° / 12°	0.7	3.9	4.4	9.3	0.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 54% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 20% of September, with mostly cloudy or overcast conditions the remaining 26%. 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 (%)	74	74	74	74	74	74	74	74	74	74	75	74	74	74	74	74	74	74	74	75	75	75	75	75	75	75	74	74	73	73
Cloudier (%)	26	26	26	26	26	26	26	26	26	26	25	26	26	26	26	26	26	26	26	25	25	25	25	25	25	25	26	26	27	27

	Clearer (%)	Cloudier (%)
1	74	26
2	74	26
3	74	26
4	74	26
5	74	26
6	74	26
7	74	26
8	74	26
9	74	26
10	74	26
11	75	25
12	74	26
13	74	26
14	74	26
15	74	26
16	74	26
17	74	26
18	74	26
19	74	26
20	75	25
21	75	25
22	75	25
23	75	25
24	75	25
25	75	25
26	75	25
27	74	26
28	74	26
29	73	27
30	73	27

Chance of precipitation in September

Any precipitationSnow

Castle Rock gets around 1.3 in of rain and snow over 6.4 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 22% and peaks near 25% on the wettest days, and about 1 day brings 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 (%)	25	25	25	25	24	24	24	24	24	24	24	23	23	23	23	23	23	22	22	21	21	20	20	20	19	19	19	19	18	18
Snow chance (%)	0	0	1	1	1	1	1	1	1	1	1	1	1	1	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2	2

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

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 99% 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 (%)	99	99	99	99	99	99	99	99	99	99	99	99	99	99	99	99	99	100	100	100	100	100	100	100	100	100	100	100	100	100
Comfortable (%)	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	0	0	0	0	0	0	0	0	0	0	0	0	0

	Dry (%)	Comfortable (%)
1	99	1
2	99	1
3	99	1
4	99	1
5	99	1
6	99	1
7	99	1
8	99	1
9	99	1
10	99	1
11	99	1
12	99	1
13	99	1
14	99	1
15	99	1
16	99	1
17	99	1
18	100	0
19	100	0
20	100	0
21	100	0
22	100	0
23	100	0
24	100	0
25	100	0
26	100	0
27	100	0
28	100	0
29	100	0
30	100	0

Wind in September

Winds average 5 mph in September.

Across September, daily wind ranges from about 5 mph on the calmest days to 6 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)	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	6	6	6	6	6	6	6	6	6	6
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	5	calm
2	5	calm
3	5	calm
4	5	calm
5	5	calm
6	5	calm
7	5	calm
8	5	calm
9	5	calm
10	5	calm
11	5	calm
12	5	calm
13	5	calm
14	5	calm
15	5	calm
16	5	calm
17	5	calm
18	5	calm
19	5	calm
20	5	calm
21	6	calm
22	6	calm
23	6	calm
24	6	calm
25	6	calm
26	6	calm
27	6	calm
28	6	calm
29	6	calm
30	6	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 5:32 AM to 6:00 AM, and sunset from 6:26 PM to 5:38 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)	5:32	5:33	5:34	5:35	5:36	5:37	5:38	5:39	5:40	5:40	5:41	5:42	5:43	5:44	5:45	5:46	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
Sunset (PM)	6:26	6:25	6:23	6:21	6:20	6:18	6:16	6:15	6:13	6:11	6:10	6:08	6:06	6:05	6:03	6:01	6:00	5:58	5:56	5:55	5:53	5:51	5:50	5:48	5:46	5:44	5:43	5:41	5:39	5:38

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	12.9	5:32	6:26
2	12.9	5:33	6:25
3	12.8	5:34	6:23
4	12.8	5:35	6:21
5	12.7	5:36	6:20
6	12.7	5:37	6:18
7	12.6	5:38	6:16
8	12.6	5:39	6:15
9	12.6	5:40	6:13
10	12.5	5:40	6:11
11	12.5	5:41	6:10
12	12.4	5:42	6:08
13	12.4	5:43	6:06
14	12.3	5:44	6:05
15	12.3	5:45	6:03
16	12.3	5:46	6:01
17	12.2	5:47	6:00
18	12.2	5:48	5:58
19	12.1	5:49	5:56
20	12.1	5:50	5:55
21	12.0	5:51	5:53
22	12.0	5:52	5:51
23	11.9	5:53	5:50
24	11.9	5:54	5:48
25	11.9	5:55	5:46
26	11.8	5:56	5:44
27	11.8	5:57	5:43
28	11.7	5:58	5:41
29	11.7	5:59	5:39
30	11.6	6:00	5:38

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.54 kWh/m².

For context, solar energy here swings from a low near 2.61 kWh/m² to a high of 7.41 kWh/m² in June across the year — September's 5.54 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)	6.0	6.0	6.0	5.9	5.9	5.9	5.8	5.8	5.8	5.7	5.7	5.6	5.6	5.6	5.5	5.5	5.5	5.4	5.4	5.4	5.3	5.3	5.2	5.2	5.2	5.1	5.1	5.0	5.0	5.0
Level	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	Bright	Bright	Bright

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

Planning a trip in September

Is September a good time to visit Castle Rock?

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

7.6

Sightseeing

1st-best month of the year

5.4

Beach & pool

4th-best month of the year

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

What to pack for Castle Rock in September

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

In September, Castle Rock sees daytime highs around 72°F and nights near 45°F. Worth packing: light clothes, a warm layer and sun protection. About 6 days see rain.

light clothesa warm layersun protection

UV index in Castle Rock in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Castle Rock peaks around July 15 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 2 (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	8	11	11	10	8	6	4	2
Level	Moderate	Moderate	Very high	High	Very high	Extreme	Extreme	Extreme	Very high	High	Moderate	Moderate

	UV index (midday)	Level
Jan	3	Moderate
Feb	4	Moderate
Mar	7	Very high
Apr	7	High
May	8	Very high
Jun	11	Extreme
Jul	11	Extreme
Aug	10	Extreme
Sep	8	Very high
Oct	6	High
Nov	4	Moderate
Dec	2	Moderate

Location & terrain

Where is Castle Rock?

Castle Rock sits at 39.4°N, 104.9°W, 6,224 ft above sea level, in United States. The nearest listed city is Parker, 11 mi away.

Topography around Castle Rock

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

Within 2 miles, the terrain around Castle Rock has only modest variations in elevation — a maximum elevation change of 646 ft around an average of 6,368 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,028 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,268 ft.

The land around Castle Rock is covered by grassland (52%) and artificial surfaces (28%) within 2 miles, grassland (74%) within 10 miles, and grassland (55%) and trees (29%) within 50 miles.

2 miles

646 ft

grassland 52%

10 miles

2,028 ft

grassland 74%

50 miles

9,268 ft

grassland 55%

treesgrasslandcroplandartificial surfacesbare terrainwater

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

September weather nearby: Parker 11 mi · Highlands Ranch 14 mi · Centennial 14 mi · Castlewood 15 mi · Southglenn 16 mi · Greenwood Village 17 mi · Littleton 19 mi · Columbine 19 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 Castle Rock (39.3722°, -104.8561°, elevation 6,224 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	77	50
2	77	50
3	76	49
4	76	49
5	76	49
6	75	48
7	75	48
8	75	47
9	74	47
10	74	47
11	74	46
12	74	46
13	73	46
14	73	45
15	73	45
16	72	45
17	72	44
18	72	44
19	71	43
20	71	43
21	71	43
22	70	42
23	70	42
24	70	42
25	69	41
26	69	41
27	69	40
28	68	40
29	68	40
30	68	39

	Clearer (%)	Cloudier (%)
1	74	26
2	74	26
3	74	26
4	74	26
5	74	26
6	74	26
7	74	26
8	74	26
9	74	26
10	74	26
11	75	25
12	74	26
13	74	26
14	74	26
15	74	26
16	74	26
17	74	26
18	74	26
19	74	26
20	75	25
21	75	25
22	75	25
23	75	25
24	75	25
25	75	25
26	75	25
27	74	26
28	74	26
29	73	27
30	73	27

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

	Dry (%)	Comfortable (%)
1	99	1
2	99	1
3	99	1
4	99	1
5	99	1
6	99	1
7	99	1
8	99	1
9	99	1
10	99	1
11	99	1
12	99	1
13	99	1
14	99	1
15	99	1
16	99	1
17	99	1
18	100	0
19	100	0
20	100	0
21	100	0
22	100	0
23	100	0
24	100	0
25	100	0
26	100	0
27	100	0
28	100	0
29	100	0
30	100	0

	Avg high (°F)	Avg low (°F)
1	77	50
2	77	50
3	76	49
4	76	49
5	76	49
6	75	48
7	75	48
8	75	47
9	74	47
10	74	47
11	74	46
12	74	46
13	73	46
14	73	45
15	73	45
16	72	45
17	72	44
18	72	44
19	71	43
20	71	43
21	71	43
22	70	42
23	70	42
24	70	42
25	69	41
26	69	41
27	69	40
28	68	40
29	68	40
30	68	39

	Clearer (%)	Cloudier (%)
1	74	26
2	74	26
3	74	26
4	74	26
5	74	26
6	74	26
7	74	26
8	74	26
9	74	26
10	74	26
11	75	25
12	74	26
13	74	26
14	74	26
15	74	26
16	74	26
17	74	26
18	74	26
19	74	26
20	75	25
21	75	25
22	75	25
23	75	25
24	75	25
25	75	25
26	75	25
27	74	26
28	74	26
29	73	27
30	73	27

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

	Dry (%)	Comfortable (%)
1	99	1
2	99	1
3	99	1
4	99	1
5	99	1
6	99	1
7	99	1
8	99	1
9	99	1
10	99	1
11	99	1
12	99	1
13	99	1
14	99	1
15	99	1
16	99	1
17	99	1
18	100	0
19	100	0
20	100	0
21	100	0
22	100	0
23	100	0
24	100	0
25	100	0
26	100	0
27	100	0
28	100	0
29	100	0
30	100	0

	Avg high (°F)	Avg low (°F)
1	77	50
2	77	50
3	76	49
4	76	49
5	76	49
6	75	48
7	75	48
8	75	47
9	74	47
10	74	47
11	74	46
12	74	46
13	73	46
14	73	45
15	73	45
16	72	45
17	72	44
18	72	44
19	71	43
20	71	43
21	71	43
22	70	42
23	70	42
24	70	42
25	69	41
26	69	41
27	69	40
28	68	40
29	68	40
30	68	39

	Clearer (%)	Cloudier (%)
1	74	26
2	74	26
3	74	26
4	74	26
5	74	26
6	74	26
7	74	26
8	74	26
9	74	26
10	74	26
11	75	25
12	74	26
13	74	26
14	74	26
15	74	26
16	74	26
17	74	26
18	74	26
19	74	26
20	75	25
21	75	25
22	75	25
23	75	25
24	75	25
25	75	25
26	75	25
27	74	26
28	74	26
29	73	27
30	73	27

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

	Dry (%)	Comfortable (%)
1	99	1
2	99	1
3	99	1
4	99	1
5	99	1
6	99	1
7	99	1
8	99	1
9	99	1
10	99	1
11	99	1
12	99	1
13	99	1
14	99	1
15	99	1
16	99	1
17	99	1
18	100	0
19	100	0
20	100	0
21	100	0
22	100	0
23	100	0
24	100	0
25	100	0
26	100	0
27	100	0
28	100	0
29	100	0
30	100	0