Guernsey, Wyoming has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 1 °C (low) to 17.5 °C (high). Annual precipitation averages 349.5 Millimeters. Guernsey 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 | -10 °C | 5.2 °C | 6.35 mm |
| February | -8.8 °C | 6.4 °C | 10.16 mm |
| March | -4.3 °C | 11.7 °C | 20.57 mm |
| April | -0.3 °C | 15.5 °C | 43.43 mm |
| May | 5.3 °C | 20.9 °C | 72.14 mm |
| June | 10.7 °C | 27.7 °C | 60.96 mm |
| July | 14.2 °C | 32.1 °C | 36.32 mm |
| August | 12.8 °C | 31.3 °C | 27.94 mm |
| September | 7.3 °C | 26.2 °C | 27.43 mm |
| October | 0.2 °C | 17.9 °C | 28.45 mm |
| November | -5.6 °C | 10.4 °C | 8.38 mm |
| December | -9.8 °C | 5.1 °C | 7.37 mm |
| Annual | 1 °C | 17.5 °C | 349.5 mm |
| 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 : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |