Casper, Wyoming has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.8 °F (low) to 60.6 °F (high). Annual precipitation averages 14.4 Inches. Casper is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.8 °F | 37.7 °F | 0.55 in. |
| February | 17.7 °F | 39.4 °F | 0.71 in. |
| March | 24.9 °F | 49.7 °F | 1.09 in. |
| April | 30.8 °F | 57.0 °F | 1.84 in. |
| May | 39.7 °F | 66.8 °F | 2.74 in. |
| June | 48.5 °F | 79.4 °F | 1.44 in. |
| July | 55.8 °F | 88.5 °F | 1.17 in. |
| August | 53.6 °F | 86.8 °F | 0.94 in. |
| September | 43.8 °F | 76.2 °F | 1.17 in. |
| October | 33.1 °F | 60.9 °F | 1.44 in. |
| November | 23.9 °F | 47.4 °F | 0.69 in. |
| December | 17.1 °F | 37.6 °F | 0.66 in. |
| Annual | 33.8 °F | 60.6 °F | 14.44 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |