Lyman, Utah has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -2.9 °C (low) to 15.3 °C (high). Annual precipitation averages 223.5 Millimeters. Lyman is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.9 °C | 3.9 °C | 13.97 mm |
| February | -10.3 °C | 5.6 °C | 12.45 mm |
| March | -6.6 °C | 9.9 °C | 14.99 mm |
| April | -3.9 °C | 13.7 °C | 12.45 mm |
| May | 0.3 °C | 18.8 °C | 19.56 mm |
| June | 4.3 °C | 25 °C | 12.95 mm |
| July | 8.3 °C | 28.1 °C | 27.94 mm |
| August | 7.3 °C | 26.6 °C | 36.07 mm |
| September | 4.1 °C | 22.9 °C | 27.69 mm |
| October | -2.9 °C | 16.2 °C | 23.11 mm |
| November | -8.9 °C | 9.4 °C | 8.38 mm |
| December | -13.3 °C | 3.7 °C | 13.97 mm |
| Annual | -2.9 °C | 15.3 °C | 223.53 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |