Evergreen, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.4 °C (low) to 13 °C (high). Annual precipitation averages 418.8 Millimeters. Evergreen is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.8 °C | -0.2 °C | 33.53 mm |
| February | -7.2 °C | 2.1 °C | 24.38 mm |
| March | -3.9 °C | 7.1 °C | 27.18 mm |
| April | -0.3 °C | 12.7 °C | 34.54 mm |
| May | 3.9 °C | 18.3 °C | 46.48 mm |
| June | 7.5 °C | 21.7 °C | 68.58 mm |
| July | 9.7 °C | 27.8 °C | 29.46 mm |
| August | 8.7 °C | 27.7 °C | 22.61 mm |
| September | 4.6 °C | 21.6 °C | 29.72 mm |
| October | -0.2 °C | 12.9 °C | 35.05 mm |
| November | -3.6 °C | 4.7 °C | 33.78 mm |
| December | -7.1 °C | -0.2 °C | 33.53 mm |
| Annual | 0.4 °C | 13 °C | 418.84 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |