Casper weather in September: Casper, Wyoming: normal highs, lows, rain and records for September
Casper in September has a normal high of 76°F and a normal low of 42°F, a daily mean of 59°F, falling from 82°F on the 1st to 68°F by the 30th. Measurable precipitation falls on 7 days in a normal September, 0.95 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 24°C and low of 6°C, 24 mm of precipitation and 4 cm of snow in September.
- NOAA stationCasper-Natrona County Airport
- Station IDUSW00024089
- Location42.90°N 106.46°W
- Elevation5,338 ft (1,627 m)
- Population58,823
- Jan 35° 15°
- Feb 38° 15°
- Mar 49° 23°
- Apr 56° 28°
- May 67° 37°
- Jun 80° 45°
- Jul 89° 53°
- Aug 87° 51°
- Sep 76° 42°
- Oct 60° 31°
- Nov 46° 22°
- Dec 35° 15°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Casper in September?
The normal high is 76°F and the normal low 42°F, for a daily mean of 58.9°F. September is 10.1°F cooler than August and 13.6°F warmer than October. September is the 4th warmest month of the year in Casper and the 6th wettest. Across the month the normal high falls 14°F, from 82°F on September 1 to 68°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 56°F and 62°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 25%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 82°F | 47°F | 20% | 8% |
| September 8 | 80°F | 45°F | 21% | 9% |
| September 15 | 76°F | 43°F | 23% | 10% |
| September 22 | 72°F | 40°F | 25% | 11% |
| September 30 | 68°F | 37°F | 25% | 11% |
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 | 82°F | 47°F | 20% | 8% | 13 h 10 min |
| September 2 | 82°F | 47°F | 20% | 8% | 13 h 10 min |
| September 3 | 82°F | 47°F | 20% | 8% | 13 h 10 min |
| September 4 | 81°F | 46°F | 20% | 8% | 13 h 10 min |
| September 5 | 81°F | 46°F | 20% | 8% | 13 h |
| September 6 | 80°F | 46°F | 21% | 8% | 13 h |
| September 7 | 80°F | 45°F | 21% | 8% | 13 h |
| September 8 | 80°F | 45°F | 21% | 9% | 12 h 50 min |
| September 9 | 79°F | 45°F | 22% | 9% | 12 h 50 min |
| September 10 | 79°F | 44°F | 22% | 9% | 12 h 50 min |
| September 11 | 78°F | 44°F | 22% | 9% | 12 h 50 min |
| September 12 | 78°F | 44°F | 23% | 9% | 12 h 40 min |
| September 13 | 77°F | 43°F | 23% | 9% | 12 h 40 min |
| September 14 | 77°F | 43°F | 23% | 10% | 12 h 40 min |
| September 15 | 76°F | 43°F | 23% | 10% | 12 h 30 min |
| September 16 | 76°F | 42°F | 24% | 10% | 12 h 30 min |
| September 17 | 75°F | 42°F | 24% | 10% | 12 h 30 min |
| September 18 | 75°F | 42°F | 24% | 10% | 12 h 30 min |
| September 19 | 74°F | 41°F | 24% | 10% | 12 h 20 min |
| September 20 | 74°F | 41°F | 25% | 10% | 12 h 20 min |
| September 21 | 73°F | 40°F | 25% | 11% | 12 h 20 min |
| September 22 | 72°F | 40°F | 25% | 11% | 12 h 10 min |
| September 23 | 72°F | 40°F | 25% | 11% | 12 h 10 min |
| September 24 | 71°F | 39°F | 25% | 11% | 12 h 10 min |
| September 25 | 71°F | 39°F | 25% | 11% | 12 h 10 min |
| September 26 | 70°F | 38°F | 25% | 11% | 12 h |
| September 27 | 70°F | 38°F | 25% | 11% | 12 h |
| September 28 | 69°F | 38°F | 25% | 11% | 12 h |
| September 29 | 68°F | 37°F | 25% | 11% | 11 h 50 min |
| September 30 | 68°F | 37°F | 25% | 11% | 11 h 50 min |
- Normal high
- 76°FSeptember average
- Normal low
- 42°FSeptember average
- Precipitation
- 0.95 inmonth total
- Days with precipitation
- 70.01 inch or more
- Snowfall
- 1.5 inmonth total
- Days at 90°F or more
- 2
- Nights at 32°F or colder
- 3
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 22
- Days at 80°F or more
- 13
- Sunshine
- 85%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024089; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain or snow in Casper in September?
On a given September day the chance of 0.01 inch or more is 23% on average, highest around September 29 (25%). In all, 0.95 in falls on 7 days of a normal September.
In a normal September in Casper, 2 days reach 90°F, 3 nights fall to freezing and snowfall averages 1.5 inches.
Snow falls on 1 day in a normal September.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024089.
How humid and windy is Casper in September?
At 3 p.m. the normal temperature is 66°F with 27% relative humidity and a dew point of 31°F; at 6 a.m. it is 42°F with 67% humidity. The wind averages 10.3 mph, most often from the west in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 42°F | 32°F | 67% | 8.5 mph | 74% |
| 9 a.m. | 54°F | 34°F | 47% | 12.5 mph | 76% |
| noon | 63°F | 33°F | 32% | 13.0 mph | 77% |
| 3 p.m. | 66°F | 31°F | 27% | 13.6 mph | 74% |
| 6 p.m. | 57°F | 33°F | 40% | 10.0 mph | 71% |
| 9 p.m. | 48°F | 33°F | 55% | 8.7 mph | 72% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024089. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for September in Casper?
The warmest September temperature on Casper's official record (since 1939) is 100°F, on September 4, 2022; the coldest is 15°F, on September 28, 1945. The wettest September brought 3.40 in (1982); the snowiest, 11.5 inches (1982).
The September mean against the 1991-2020 normal of 58.9°F: 2021 61.7°F (+2.8), 2022 62.3°F (+3.4), 2023 61.2°F (+2.3), 2024 63.3°F (+4.4), 2025 61.5°F (+2.6), 2026 62.7°F (+3.8). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 61.7°F | +2.8°F | 0.79 in |
| 2022 | 62.3°F | +3.4°F | 0.81 in |
| 2023 | 61.2°F | +2.3°F | 0.59 in |
| 2024 | 63.3°F | +4.4°F | 0.24 in |
| 2025 | 61.5°F | +2.6°F | 2.55 in |
| 2026 | 62.7°F | +3.8°F | 0.76 in |
Source: records: ACIS, NWS threaded record CPRthr; recent months: ACIS, station USW00024089. Records and recent months use complete months only.
How does September in Casper compare across Wyoming?
Across the 71 places PlainClimate covers in Wyoming, September normal highs run from 65°F in Sundance to 81°F in Yoder; Casper's is 76°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.