East Helena, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 32.5 °F (low) to 57.5 °F (high). Annual precipitation averages 12.7 Inches. East Helena is located in USDA Plant Hardiness Zone 4b. 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 | 14.4 °F | 33.6 °F | 0.38 in. |
| February | 17.1 °F | 37.6 °F | 0.52 in. |
| March | 23.6 °F | 46.9 °F | 0.6 in. |
| April | 31.0 °F | 55.9 °F | 1.35 in. |
| May | 39.4 °F | 65.3 °F | 2.56 in. |
| June | 46.5 °F | 73.8 °F | 2.2 in. |
| July | 52.1 °F | 84.9 °F | 1.21 in. |
| August | 50.1 °F | 84.3 °F | 1.11 in. |
| September | 42.9 °F | 72.9 °F | 1.03 in. |
| October | 33.1 °F | 57.7 °F | 0.86 in. |
| November | 23.9 °F | 43.4 °F | 0.57 in. |
| December | 15.8 °F | 34.2 °F | 0.26 in. |
| Annual | 32.5 °F | 57.5 °F | 12.65 in. |
| 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 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |