Mills, Wyoming has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.8 °F (low) to 60.7 °F (high). Annual precipitation averages 16.2 Inches. Mills 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 | 17.0 °F | 37.7 °F | 0.71 in. |
| February | 17.7 °F | 39.5 °F | 0.88 in. |
| March | 24.8 °F | 49.8 °F | 1.34 in. |
| April | 30.8 °F | 57.1 °F | 1.98 in. |
| May | 39.6 °F | 67.0 °F | 2.98 in. |
| June | 48.5 °F | 79.6 °F | 1.67 in. |
| July | 55.8 °F | 88.7 °F | 1.13 in. |
| August | 53.6 °F | 87.0 °F | 0.93 in. |
| September | 43.8 °F | 76.4 °F | 1.12 in. |
| October | 33.0 °F | 61.0 °F | 1.76 in. |
| November | 23.9 °F | 47.4 °F | 0.85 in. |
| December | 17.2 °F | 37.7 °F | 0.83 in. |
| Annual | 33.8 °F | 60.7 °F | 16.18 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 |