Lyman, Wyoming has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 28.5 °F (low) to 56.2 °F (high). Annual precipitation averages 10.4 Inches. Lyman is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Jun. 1 - Jun. 10 through the first frost around Sep.1 - Sep. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 10.2 °F | 32.1 °F | 0.52 in. |
| February | 11.7 °F | 34.1 °F | 0.54 in. |
| March | 20.4 °F | 44.2 °F | 0.68 in. |
| April | 26.8 °F | 53.9 °F | 1.06 in. |
| May | 34.8 °F | 63.8 °F | 1.4 in. |
| June | 42.2 °F | 74.8 °F | 0.94 in. |
| July | 49.3 °F | 83.3 °F | 0.88 in. |
| August | 47.7 °F | 81.7 °F | 0.8 in. |
| September | 39.2 °F | 72.3 °F | 1.18 in. |
| October | 29.4 °F | 58.6 °F | 1.02 in. |
| November | 19.1 °F | 43.0 °F | 0.77 in. |
| December | 10.7 °F | 32.3 °F | 0.59 in. |
| Annual | 28.5 °F | 56.2 °F | 10.38 in. |
| Average First Frost Date | Sep.1 - Sep. 10 |
| Average Last Frost Date | Jun. 1 - Jun. 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 | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |