Helmville, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 26.2 °F (low) to 55.2 °F (high). Annual precipitation averages 13.8 Inches. Helmville is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 10.5 °F | 31.5 °F | 1.0 in. |
| February | 12.0 °F | 35.9 °F | 0.85 in. |
| March | 19.3 °F | 44.9 °F | 0.68 in. |
| April | 26.1 °F | 53.8 °F | 1.04 in. |
| May | 33.0 °F | 63.8 °F | 1.72 in. |
| June | 39.5 °F | 71.1 °F | 2.2 in. |
| July | 43.3 °F | 82.2 °F | 0.95 in. |
| August | 41.5 °F | 81.8 °F | 0.96 in. |
| September | 34.5 °F | 71.2 °F | 1.11 in. |
| October | 26.1 °F | 55.5 °F | 1.07 in. |
| November | 18.2 °F | 40.3 °F | 1.15 in. |
| December | 10.8 °F | 30.8 °F | 1.09 in. |
| Annual | 26.2 °F | 55.2 °F | 13.82 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |