Climateby Month

Casper, WY climate by month

NOAA 1991-2020 normals · 5,105 ft elevation

Casper has hot summers and cold and snowy winters. Highs peak at 89°F in July and fall to 35°F in December. Wet days are spread through the year, from about 6 to 11 a month. Normal snowfall is about 72 in a year. By our comfort score the best month is May.

Warmest month
89°F
July normal high
Coldest month
15°F
December normal low
Wet days a year
91
12.2 in of precipitation
Snow a year
71.8 in
normal snowfall

How warm is Casper?

Normal highs range from 35°F in December to 89°F in July.

0°20°40°60°80°100° January: normal high 35°F (2°C), low 15°F (-9°C) 35° 15° February: normal high 38°F (3°C), low 15°F (-9°C) March: normal high 49°F (9°C), low 23°F (-5°C) April: normal high 56°F (13°C), low 28°F (-2°C) May: normal high 67°F (19°C), low 37°F (3°C) June: normal high 80°F (27°C), low 45°F (7°C) July: normal high 89°F (32°C), low 53°F (12°C) 89° 53° August: normal high 87°F (31°C), low 51°F (11°C) September: normal high 76°F (24°C), low 42°F (6°C) October: normal high 60°F (16°C), low 31°F (-1°C) November: normal high 46°F (8°C), low 22°F (-6°C) December: normal high 35°F (2°C), low 15°F (-9°C) JFMAMJJASOND

Bars run from the normal low to the normal high for each month.

How rainy is Casper?

May has the most wet days (about 11); the year brings about 12 in of precipitation.

January: 6 wet days February: 7 wet days March: 8 wet days April: 10 wet days May: 11 wet days 11 June: 9 wet days July: 7 wet days August: 6 wet days 6 September: 7 wet days October: 8 wet days November: 6 wet days December: 7 wet days JFMAMJJASOND

Wet day: at least 0.01 in of rain or melted snow, counted from daily records 1991-2020.

How much does it snow?

Normal snowfall is 71.8 in a year, most of it in December.

January: 9.0 in of snow February: 10.9 in of snow March: 10.3 in of snow April: 10.5 in of snow May: 2.6 in of snow June: 0.1 in of snow July: 0.0 in of snow 0.0 August: 0.0 in of snow September: 1.5 in of snow October: 7.0 in of snow November: 8.9 in of snow December: 11.0 in of snow 11.0 JFMAMJJASOND

How humid is Casper?

Muggy days (dew point 65°F or higher) are rare in any month.

January: 0 muggy days 0 February: 0 muggy days March: 0 muggy days April: 0 muggy days May: 0 muggy days June: 0 muggy days July: 0 muggy days August: 0 muggy days September: 0 muggy days October: 0 muggy days November: 0 muggy days December: 0 muggy days JFMAMJJASOND

Muggy day: daily mean dew point of 65°F or higher, from hourly observations 1991-2020 at Natrona County International Airport, 8.4 mi WNW of the city center.

How much daylight?

Daylight ranges from about 9.1 hours in December to 15.3 hours in June.

January: 9.4 hours of daylight February: 10.6 hours of daylight March: 11.9 hours of daylight April: 13.4 hours of daylight May: 14.7 hours of daylight June: 15.3 hours of daylight 15.3 July: 15.0 hours of daylight August: 13.9 hours of daylight September: 12.5 hours of daylight October: 11.0 hours of daylight November: 9.8 hours of daylight December: 9.1 hours of daylight 9.1 JFMAMJJASOND
See all numbers
Monthly climate normals and day counts for Casper, 1991-2020
MonthHighLowPrecip.Wet daysSnowMuggy daysDaylight
January 35°F15°F 0.5 in6 9.0 in 0 9.4 h
February 38°F15°F 0.6 in7 10.9 in 0 10.6 h
March 49°F23°F 0.8 in8 10.3 in 0 11.9 h
April 56°F28°F 1.4 in10 10.5 in 0 13.4 h
May 67°F37°F 2.2 in11 2.6 in 0 14.7 h
June 80°F45°F 1.3 in9 0.1 in 0 15.3 h
July 89°F53°F 1.2 in7 0.0 in 0 15.0 h
August 87°F51°F 0.8 in6 0.0 in 0 13.9 h
September 76°F42°F 0.9 in7 1.5 in 0 12.5 h
October 60°F31°F 1.2 in8 7.0 in 0 11.0 h
November 46°F22°F 0.6 in6 8.9 in 0 9.8 h
December 35°F15°F 0.6 in7 11.0 in 0 9.1 h

High and low: NOAA 1991-2020 normal daily high and low. Wet days: at least 0.01 in of rain or melted snow. Muggy days: daily mean dew point 65°F or higher.

Best months to visit Casper

By our comfort score, the best month is May.

Comfort score by month (0-100) and its parts, in days per month
MonthScoreComfortableNotable rainHot or cold
Jan 320220
Feb 360216
Mar 49338
Apr 61853
May 741551
Jun 701345
Jul 513317
Aug 534213
Sep 671433
Oct 611233
Nov 42229
Dec 300221

Score = 40 × share of comfortable days + 25 × share of days without notable rain + 20 × share of days neither hot (90°F+) nor cold (high 40°F or below) + 15 × daylight. How the score works.

Frost dates in Casper

The last spring frost typically comes around May 26, and the first fall frost around Sep 22, leaving 117 frost-free days in a typical year.

Frost and freeze dates for Casper
Typical date1 year in 10
Last spring frost (32°F)May 26after Jun 10
First fall frost (32°F)Sep 22before Sep 5
Last hard freeze (28°F)May 11after May 27
First hard freeze (28°F)Oct 2before Sep 17
Frost-free season117 daysunder 96 days

"Typical" is the date with a 50% chance of a later spring frost (or earlier fall frost). Planting after the "1 year in 10" spring date gives a 90% chance of no further frost. The Old Farmer's Almanac publishes 30% dates, which fall between our typical and 1-in-10 dates.

Station: Casper Natrona Co Airport (USW00024089), NOAA 1991-2020 freeze probabilities. Frost dates for every city in Wyoming.

Hottest and coldest readings, 1991-2020

The highest reading was 104°F (July 29, 2006, and 1 other day); the lowest was -33°F (December 8, 2016).

From the temperature station's daily records with NOAA quality flags removed. Not an all-time record.

Near Casper

Similar climates elsewhere

Where the numbers come from

  • Temperature, rain, snowfall, snow depth, frost dates, humidity and wind by hour and cloud cover: Casper Natrona Co Airport (USW00024089), 7.9 mi WNW of the city center, 5,338 ft (233 ft higher than the city). NOAA normals and daily records, 1991-2020.
  • Daily humidity and wind: Natrona County International Airport (725690-24089), 8.4 mi WNW of the city center, 5,319 ft (214 ft higher than the city). Hourly observations, 1991-2020.

Distances from the city center (USGS). Methodology · Report an error