Castle Rock weather in September: Castle Rock, Colorado: normal highs, lows, rain and records for September
Castle Rock in September has a normal high of 77°F and a normal low of 47°F, a daily mean of 62°F, falling from 81°F on the 1st to 71°F by the 30th. Measurable precipitation falls on 6 days in a normal September, 1.39 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 25°C and low of 8°C, 35 mm of precipitation and 1 cm of snow in September.
- NOAA stationCastle Rock
- Station IDUSC00051401
- Location39.41°N 104.91°W
- Elevation6,185 ft (1,885 m)
- Population83,213
- Jan 46° 18°
- Feb 47° 20°
- Mar 54° 27°
- Apr 59° 33°
- May 68° 42°
- Jun 80° 51°
- Jul 86° 56°
- Aug 84° 55°
- Sep 77° 47°
- Oct 65° 35°
- Nov 54° 26°
- Dec 46° 18°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Castle Rock in September?
The normal high is 77°F and the normal low 47°F, for a daily mean of 61.7°F. September is 7.4°F cooler than August and 12.0°F warmer than October. September is the 4th warmest month of the year in Castle Rock and the 7th wettest. Across the month the normal high falls 10°F, from 81°F on September 1 to 71°F on September 30. From one year to the next September's mean temperature typically moves about 2.6°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 59°F and 64°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 26%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 81°F | 52°F | 26% | 13% |
| September 8 | 80°F | 50°F | 23% | 12% |
| September 15 | 77°F | 47°F | 20% | 11% |
| September 22 | 75°F | 44°F | 18% | 10% |
| September 30 | 71°F | 41°F | 16% | 9% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 81°F | 52°F | 26% | 13% | 13 h 10 min |
| September 2 | 81°F | 52°F | 25% | 13% | 13 h |
| September 3 | 81°F | 51°F | 25% | 13% | 13 h |
| September 4 | 81°F | 51°F | 24% | 12% | 13 h |
| September 5 | 80°F | 51°F | 24% | 12% | 13 h |
| September 6 | 80°F | 50°F | 24% | 12% | 12 h 50 min |
| September 7 | 80°F | 50°F | 23% | 12% | 12 h 50 min |
| September 8 | 80°F | 50°F | 23% | 12% | 12 h 50 min |
| September 9 | 79°F | 49°F | 23% | 12% | 12 h 50 min |
| September 10 | 79°F | 49°F | 22% | 12% | 12 h 40 min |
| September 11 | 79°F | 49°F | 22% | 11% | 12 h 40 min |
| September 12 | 78°F | 48°F | 22% | 11% | 12 h 40 min |
| September 13 | 78°F | 48°F | 21% | 11% | 12 h 40 min |
| September 14 | 78°F | 48°F | 21% | 11% | 12 h 30 min |
| September 15 | 77°F | 47°F | 20% | 11% | 12 h 30 min |
| September 16 | 77°F | 47°F | 20% | 11% | 12 h 30 min |
| September 17 | 77°F | 46°F | 20% | 10% | 12 h 30 min |
| September 18 | 76°F | 46°F | 19% | 10% | 12 h 20 min |
| September 19 | 76°F | 45°F | 19% | 10% | 12 h 20 min |
| September 20 | 75°F | 45°F | 19% | 10% | 12 h 20 min |
| September 21 | 75°F | 45°F | 18% | 10% | 12 h 20 min |
| September 22 | 75°F | 44°F | 18% | 10% | 12 h 10 min |
| September 23 | 74°F | 44°F | 18% | 10% | 12 h 10 min |
| September 24 | 74°F | 43°F | 18% | 10% | 12 h 10 min |
| September 25 | 73°F | 43°F | 17% | 10% | 12 h 10 min |
| September 26 | 73°F | 42°F | 17% | 9% | 12 h |
| September 27 | 72°F | 42°F | 17% | 9% | 12 h |
| September 28 | 72°F | 41°F | 16% | 9% | 12 h |
| September 29 | 72°F | 41°F | 16% | 9% | 11 h 50 min |
| September 30 | 71°F | 41°F | 16% | 9% | 11 h 50 min |
- Normal high
- 77°FSeptember average
- Normal low
- 47°FSeptember average
- Precipitation
- 1.39 inmonth total
- Days with precipitation
- 60.01 inch or more
- Snowfall
- 0.4 inmonth total
- Days at 90°F or more
- 2
- Nights at 32°F or colder
- 1
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 25
- Days at 80°F or more
- 14
- Sunshine
- 85%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00051401; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain or snow in Castle Rock in September?
On a given September day the chance of 0.01 inch or more is 20% on average, highest around September 1 (26%). In all, 1.39 in falls on 6 days of a normal September.
In a normal September in Castle Rock, 2 days reach 90°F, 1 nights fall to freezing and snowfall averages 0.4 inches.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00051401.
What are the records for September in Castle Rock?
The warmest September temperature on this station's record (since 1893) is 101°F, on September 12, 2021; the coldest is 11°F, on September 28, 1984. The wettest September brought 6.45 in (2013); the snowiest, 11.5 inches (1971).
The September mean against the 1991-2020 normal of 61.7°F: 2021 72.2°F (+10.5), 2022 65.1°F (+3.4), 2023 63.1°F (+1.4), 2024 65.6°F (+3.9), 2025 62.7°F (+1.0). 5 of 5 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 72.2°F | +10.5°F | 0.89 in |
| 2022 | 65.1°F | +3.4°F | 1.38 in |
| 2023 | 63.1°F | +1.4°F | 1.88 in |
| 2024 | 65.6°F | +3.9°F | 0.70 in |
| 2025 | 62.7°F | +1.0°F | 2.00 in |
Source: records: ACIS, station USC00051401; recent months: ACIS, station USC00051401. Records and recent months use complete months only.
How does September in Castle Rock compare across Colorado?
Across the 125 places PlainClimate covers in Colorado, September normal highs run from 62°F in Leadville to 86°F in Lamar; Castle Rock's is 77°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.
Other months and places
- Castle Rock in August84°F by day, 55°F at night
- Castle Rock in October65°F by day, 35°F at night
- Castle Rock through the yearEvery month, frost dates, records and recent years
- Colorado in SeptemberThe statewide normal and the warmest and coolest places
- Lamar: Colorado's warmest Septembernormal high 86°F