Hanna, Wyoming has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 29.1 °F (low) to 56.1 °F (high). Annual precipitation averages 12.6 Inches. Hanna is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 12.6 °F | 33.1 °F | 0.67 in. |
| February | 13.7 °F | 35.0 °F | 0.67 in. |
| March | 21.1 °F | 44.3 °F | 0.89 in. |
| April | 26.7 °F | 52.6 °F | 1.44 in. |
| May | 34.9 °F | 63.2 °F | 1.9 in. |
| June | 42.9 °F | 75.2 °F | 1.1 in. |
| July | 49.4 °F | 83.3 °F | 0.95 in. |
| August | 47.4 °F | 81.2 °F | 0.94 in. |
| September | 39.0 °F | 71.9 °F | 1.0 in. |
| October | 29.0 °F | 57.3 °F | 1.34 in. |
| November | 20.3 °F | 43.1 °F | 0.93 in. |
| December | 12.4 °F | 33.0 °F | 0.81 in. |
| Annual | 29.1 °F | 56.1 °F | 12.64 in. |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |