Fontenelle, Wyoming has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -4.2 °C (low) to 12.7 °C (high). Annual precipitation averages 192.3 Millimeters. Fontenelle is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around Jun. 11 - Jun. 20 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.6 °C | -1.5 °C | 8.64 mm |
| February | -14.6 °C | 0.3 °C | 8.38 mm |
| March | -8.3 °C | 6.2 °C | 13.46 mm |
| April | -4 °C | 11.4 °C | 21.34 mm |
| May | 0.7 °C | 17 °C | 37.85 mm |
| June | 4.6 °C | 23.2 °C | 19.3 mm |
| July | 8.1 °C | 28.1 °C | 11.68 mm |
| August | 6.8 °C | 27.2 °C | 17.78 mm |
| September | 1.9 °C | 21.9 °C | 21.84 mm |
| October | -3.7 °C | 13.8 °C | 16.51 mm |
| November | -9.6 °C | 5.6 °C | 8.13 mm |
| December | -15.3 °C | -1 °C | 7.37 mm |
| Annual | -4.2 °C | 12.7 °C | 192.28 mm |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | Jun. 11 - Jun. 20 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |