Elmo, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.7 °F (low) to 56.6 °F (high). Annual precipitation averages 15.8 Inches. Elmo is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 19.6 °F | 33.6 °F | 1.16 in. |
| February | 20.4 °F | 37.2 °F | 0.95 in. |
| March | 25.8 °F | 46.2 °F | 1.05 in. |
| April | 31.7 °F | 55.7 °F | 1.51 in. |
| May | 39.4 °F | 64.9 °F | 1.65 in. |
| June | 45.9 °F | 71.7 °F | 2.56 in. |
| July | 50.6 °F | 82.9 °F | 1.29 in. |
| August | 49.4 °F | 82.9 °F | 0.67 in. |
| September | 42.1 °F | 72.2 °F | 1.15 in. |
| October | 33.1 °F | 56.3 °F | 1.4 in. |
| November | 26.1 °F | 41.7 °F | 1.38 in. |
| December | 20.4 °F | 33.4 °F | 1.05 in. |
| Annual | 33.7 °F | 56.6 °F | 15.82 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |