Bar Nunn, Wyoming has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.7 °C (low) to 15.6 °C (high). Annual precipitation averages 381.8 Millimeters. Bar Nunn 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 | -8.8 °C | 2.7 °C | 15.49 mm |
| February | -8.3 °C | 3.7 °C | 20.07 mm |
| March | -4.3 °C | 9.4 °C | 30.73 mm |
| April | -1 °C | 13.6 °C | 48.01 mm |
| May | 4 °C | 19 °C | 69.85 mm |
| June | 8.8 °C | 26.1 °C | 38.61 mm |
| July | 12.8 °C | 31.1 °C | 29.72 mm |
| August | 11.7 °C | 30.2 °C | 22.61 mm |
| September | 6.3 °C | 24.3 °C | 28.19 mm |
| October | 0.3 °C | 15.7 °C | 40.64 mm |
| November | -4.8 °C | 8.2 °C | 19.81 mm |
| December | -8.7 °C | 2.7 °C | 18.03 mm |
| Annual | 0.7 °C | 15.6 °C | 381.76 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |