Casper, WY Weather OverviewScoresFors & AgainstsWeatherPhotos Average Temperature Jan 37 °F3 °C Feb 29 °F-2 °C Mar 39 °F4 °C Apr 56 °F14 °C May 55 °F13 °C Jun 73 °F23 °C Jul 82 °F28 °C Aug 82 °F28 °C Sep 73 °F23 °C Oct 52 °F11 °C Nov 43 °F6 °C Dec 36 °F2 °C Humidity Jan 52% Feb 60% Mar 60% Apr 52% May 63% Jun 48% Jul 46% Aug 42% Sep 42% Oct 49% Nov 62% Dec 56% Rain Jan 21mm Feb 20mm Mar 39mm Apr 43mm May 90mm Jun 78mm Jul 26mm Aug 28mm Sep 24mm Oct 31mm Nov 20mm Dec 17mm Clouds Jan 39% Feb 40% Mar 41% Apr 48% May 63% Jun 24% Jul 16% Aug 18% Sep 17% Oct 32% Nov 37% Dec 33% Air quality US AQI Jan 8 Feb 21 Mar 21 Apr 21 May 21 Jun 21 Jul 19 Aug 14 Sep 11 Oct 9 Nov 10 Dec 9 Sun Jan 2UVI Feb 2UVI Mar 4UVI Apr 6UVI May 6UVI Jun 9UVI Jul 10UVI Aug 9UVI Sep 7UVI Oct 4UVI Nov 2UVI Dec 1UVI