Casper, Wyoming climate: Normal weather by month, frost dates and records
Casper's normal year runs from 15°F December nights to 89°F July afternoons, with 12.2 inches of precipitation and 72 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.6°C, December lows of −10°C, July highs of 32°C, 310 mm of precipitation a year.
- NOAA stationCasper-Natrona County Airport
- Station IDUSW00024089
- Location42.90°N 106.46°W
- Elevation5,338 ft (1,627 m)
- Population58,823
On October 22, the normal high in Casper is 57°F and the normal low 29°F, and the chance of measurable rain or snow is 22%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Casper.
- 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.
What is the weather like in Casper each month?
July is the warmest month, with normal highs of 89°F; December the coldest, with normal lows of 15°F. The most precipitation falls in May (2.21 in), the least in January (0.49 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 35°F | 15°F | 25.1°F | 0.49 | 9.0 | 6 | <1 | 29 | 9 h 20 min |
| February | 38°F | 15°F | 26.6°F | 0.56 | 10.9 | 7 | <1 | 26 | 10 h 30 min |
| March | 49°F | 23°F | 35.8°F | 0.84 | 10.3 | 8 | <1 | 26 | 11 h 50 min |
| April | 56°F | 28°F | 42.3°F | 1.41 | 10.5 | 10 | <1 | 21 | 13 h 20 min |
| May | 67°F | 37°F | 52.0°F | 2.21 | 2.6 | 11 | <1 | 8 | 14 h 40 min |
| June | 80°F | 45°F | 62.5°F | 1.34 | 0.1 | 9 | 5 | <1 | 15 h 20 min |
| July | 89°F | 53°F | 71.0°F | 1.19 | 0.0 | 7 | 17 | <1 | 15 h |
| August | 87°F | 51°F | 69.0°F | 0.79 | 0.0 | 6 | 13 | <1 | 14 h |
| September | 76°F | 42°F | 58.9°F | 0.95 | 1.5 | 7 | 2 | 3 | 12 h 30 min |
| October | 60°F | 31°F | 45.3°F | 1.19 | 7.0 | 8 | <1 | 17 | 11 h 10 min |
| November | 46°F | 22°F | 34.0°F | 0.64 | 8.9 | 6 | <1 | 24 | 9 h 50 min |
| December | 35°F | 15°F | 24.8°F | 0.61 | 11.0 | 7 | <1 | 29 | 9 h |
| Year (annual) | 60°F | 32°F | 45.6°F | 12.22 | 71.8 | 91 | 38 | 183 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 2°C | −9°C | −3.8°C | 12 mm | 23 cm |
| February | 3°C | −9°C | −3.0°C | 14 mm | 28 cm |
| March | 9°C | −5°C | 2.1°C | 21 mm | 26 cm |
| April | 13°C | −2°C | 5.7°C | 36 mm | 27 cm |
| May | 19°C | 3°C | 11.1°C | 56 mm | 7 cm |
| June | 26°C | 7°C | 16.9°C | 34 mm | 0 cm |
| July | 32°C | 12°C | 21.7°C | 30 mm | 0 cm |
| August | 30°C | 11°C | 20.6°C | 20 mm | 0 cm |
| September | 24°C | 6°C | 14.9°C | 24 mm | 4 cm |
| October | 15°C | −1°C | 7.4°C | 30 mm | 18 cm |
| November | 8°C | −6°C | 1.1°C | 16 mm | 23 cm |
| December | 2°C | −10°C | −4.0°C | 15 mm | 28 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024089; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Casper?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September has the fewest days with rain (7).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024089.
When is the last frost in Casper?
In Casper, the last spring frost (32°F) comes after May 26 in half of years and after June 10 in one year in ten; the first autumn frost comes before September 22 in half of years and before September 5 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- May 261 year in 10 after June 10; 9 in 10 after May 12
- First autumn frost, half of years before
- September 221 year in 10 before September 5; 9 in 10 before October 4
NOAA puts the median frost-free season at 117 days, and the season without a hard freeze (28°F) at 141 days.
A hard freeze (28°F) comes after May 11 in half of springs and before October 2 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Casper in zone 5a in ZIP code 82644, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Casper's NOAA station is in zone 4b: the coldest night of a typical year reaches −21°F (30 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Wyoming · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00024089; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Casper?
In a normal year in Casper, 38 days a year reach 90°F (1 of them 100°F or more), 183 nights fall to 32°F or colder and 91 days bring measurable precipitation.
- Days at 90°F or more
- 38a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 183a normal year
- Days that stay below freezing
- 41high of 32°F or less
- Days with 0.01 inch of precipitation
- 91a normal year
- Days with 1 inch of snow or more
- 22a normal year
The highest temperature in Casper's official record (kept by the National Weather Service since 1939) is 104°F, on July 12, 1954; the lowest is −42°F, on December 22, 2022.
The wettest calendar year on that record is 1982, with 20.48 in; the snowiest season is 1982–83, with 151.6 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00024089; records: ACIS (NOAA Regional Climate Centers), NWS threaded record CPRthr. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Casper, and how clear are its skies?
The summer (June-August) dew point averages 42°F. The muggiest month is July, with an average dew point of 45°F; the driest air comes in December (13°F). December is the windiest month (15.5 mph on average), and June has the most clear or nearly clear hours (81%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 15°F | 62% | 51% | 14.3 mph | 65% | 21% |
| February | 16°F | 60% | 43% | 13.3 mph | 65% | 21% |
| March | 23°F | 55% | 33% | 12.2 mph | 58% | 24% |
| April | 30°F | 55% | 32% | 10.9 mph | 58% | 23% |
| May | 40°F | 54% | 31% | 10.0 mph | 66% | 16% |
| June | 43°F | 44% | 20% | 9.4 mph | 81% | 6% |
| July | 45°F | 42% | 20% | 8.8 mph | 81% | 6% |
| August | 39°F | 40% | 19% | 9.5 mph | 81% | 6% |
| September | 33°F | 49% | 27% | 10.3 mph | 73% | 15% |
| October | 23°F | 54% | 35% | 12.3 mph | 68% | 21% |
| November | 16°F | 58% | 46% | 14.6 mph | 68% | 19% |
| December | 13°F | 62% | 54% | 15.5 mph | 69% | 18% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024089. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is Casper?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Casper, 4.6 kWh per square metre a day. July is the sunniest month (86%) and December the cloudiest (68%). Among the 459 U.S. places of 50,000 or more, that ranks tied 210th (with 32 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 73% | 2.1 |
| February | 70% | 3.0 |
| March | 72% | 4.2 |
| April | 72% | 5.4 |
| May | 75% | 6.4 |
| June | 84% | 7.5 |
| July | 86% | 7.3 |
| August | 86% | 6.4 |
| September | 85% | 5.2 |
| October | 77% | 3.5 |
| November | 75% | 2.4 |
| December | 68% | 1.7 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Casper need?
A normal year in Casper brings 7,486 heating degree days, 39% more than the median U.S. place (5,373), and 443 cooling degree days, 51% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,156 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,237 | 0 |
| February | 1,075 | 0 |
| March | 907 | 0 |
| April | 683 | 0 |
| May | 409 | 4 |
| June | 126 | 51 |
| July | 14 | 200 |
| August | 31 | 157 |
| September | 214 | 31 |
| October | 611 | 1 |
| November | 932 | 0 |
| December | 1,248 | 0 |
| Year (annual) | 7,486 | 443 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024089. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Casper been warmer than normal lately?
2025 averaged 47.1°F, 1.5°F above the 1991-2020 normal of 45.6°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 46.3°F | +0.7°F | 14.52 | 108.1 |
| 2022 | 44.4°F | −1.2°F | 13.36 | 100.7 |
| 2023 | 44.7°F | −0.9°F | 15.36 | 115.7 |
| 2024 | 47.6°F | +2.0°F | 9.28 | 30.0 |
| 2025 | 47.1°F | +1.5°F | 12.05 | – |
Over 78 complete years from 1940 to 2025, the station's annual mean temperature rose at a fitted 3.6°F per century (+0.20°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00024089; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Casper's climate compare?
Casper is warmer than 49 of the other 70 places with their own NOAA record in Wyoming, and wetter than 33. Across the 7,247 U.S. stations with normals, its annual mean of 45.6°F is warmer than 22%.
In the Köppen classification computed from these normals, Casper is Dfb: continental, no dry season, warm summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Casper share this climate record?
12 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Mills, WY4,584 people · 5 mi SE
- Bar Nunn, WY3,019 people · 6 mi E
- Evansville, WY2,837 people · 10 mi E
- Hartrandt, WY1,005 people · 6 mi E
- Vista West, WY917 people · 3 mi SE
- Red Butte, WY799 people · 6 mi S
- Homa Hills, WY260 people · 8 mi NE
- Meadow Acres, WY138 people · 19 mi E
- Bessemer Bend, WY119 people · 10 mi S
- Brookhurst, WY96 people · 12 mi E
- Antelope Hills, WY0 people · 15 mi NE
- Mountain View, WY0 people · 3 mi SE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Casper's other NOAA stations record?
2 more NOAA stations keep 1991-2020 normals in or near Casper. This page uses Casper-Natrona County Airport; the others differ by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Casper (1 mi SW) USC00481572 | 10 mi E | 5,143 ft | 47.1°F | 16°F | 87°F | 15.9 | – | May 12 |
| Casper Wastewater Treatment Plant USC00481569 | 9 mi E | 5,097 ft | 47.4°F | 17°F | 88°F | 13.4 | – | May 10 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Casper's climate
What is the coldest month in Casper?
December, with a normal high of 35°F and a normal low of 15°F. The warmest is July (89°F by day, 53°F at night).
Does it snow in Casper?
Yes: 72 inches in a normal year, falling on 46 days with 0.1 inch or more, the most in December (11.0 inches).
What is the rainiest month in Casper?
May, with 2.21 in of precipitation in a normal year; the driest is January with 0.49 in.
What plant hardiness zone is Casper in?
The USDA's 2023 map puts Casper in zone 5a in ZIP code 82644, the nearest ZIP area. By the same method at Casper's NOAA station, the coldest night of a typical year reaches −21°F (30 years, 1991-2020): zone 4b.
How late can frost come in Casper?
In half of years the last 32°F night comes after May 26; in one year in ten it comes after June 10. Waiting until June 10 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Casper in OctoberThis month day by day, its records and recent years
- Wyoming climateThe statewide normals and every place in the state
- Bates Creek #2, WY20 miles from this station, 44.0°F a year
- Powder River, WY28 miles from this station, 44.6°F a year
- Powder River (School), WY28 miles from this station, 43.7°F a year
- Pathfinder Dam, WY35 miles from this station, 46.3°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made