Alta, Wyoming has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -3.3 °C (low) to 11.2 °C (high). Annual precipitation averages 645.9 Millimeters. Alta is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Jun. 11 - Jun. 20 through the first frost around Sep.1 - Sep. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.4 °C | -1.9 °C | 66.04 mm |
| February | -12.3 °C | 0.1 °C | 49.02 mm |
| March | -8 °C | 4.7 °C | 56.13 mm |
| April | -3.8 °C | 9.3 °C | 61.47 mm |
| May | 0.7 °C | 15.3 °C | 75.44 mm |
| June | 4.3 °C | 20.4 °C | 57.66 mm |
| July | 7.4 °C | 26.2 °C | 34.54 mm |
| August | 6.4 °C | 25.7 °C | 33.02 mm |
| September | 2.4 °C | 20.4 °C | 46.23 mm |
| October | -2.4 °C | 11.9 °C | 53.59 mm |
| November | -8.2 °C | 3.7 °C | 51.82 mm |
| December | -12.9 °C | -2 °C | 60.96 mm |
| Annual | -3.3 °C | 11.2 °C | 645.92 mm |
| Average First Frost Date | Sep.1 - Sep. 10 |
| Average Last Frost Date | Jun. 11 - Jun. 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 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |