Gillette, Wyoming has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 33.1 °F (low) to 58.4 °F (high). Annual precipitation averages 17.7 Inches. Gillette is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.8 °F | 35.1 °F | 0.65 in. |
| February | 15.4 °F | 36.8 °F | 0.74 in. |
| March | 23.2 °F | 47.2 °F | 1.09 in. |
| April | 30.4 °F | 55.1 °F | 2.28 in. |
| May | 39.7 °F | 64.2 °F | 3.07 in. |
| June | 49.0 °F | 76.2 °F | 2.45 in. |
| July | 55.9 °F | 85.9 °F | 1.88 in. |
| August | 54.5 °F | 85.1 °F | 1.2 in. |
| September | 44.9 °F | 74.8 °F | 1.24 in. |
| October | 33.1 °F | 59.1 °F | 1.53 in. |
| November | 22.6 °F | 45.6 °F | 0.63 in. |
| December | 14.8 °F | 35.9 °F | 0.9 in. |
| Annual | 33.1 °F | 58.4 °F | 17.66 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |