Elmo, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1 °C (low) to 13.7 °C (high). Annual precipitation averages 401.8 Millimeters. 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 | -6.9 °C | 0.9 °C | 29.46 mm |
| February | -6.4 °C | 2.9 °C | 24.13 mm |
| March | -3.4 °C | 7.9 °C | 26.67 mm |
| April | -0.2 °C | 13.2 °C | 38.35 mm |
| May | 4.1 °C | 18.3 °C | 41.91 mm |
| June | 7.7 °C | 22.1 °C | 65.02 mm |
| July | 10.3 °C | 28.3 °C | 32.77 mm |
| August | 9.7 °C | 28.3 °C | 17.02 mm |
| September | 5.6 °C | 22.3 °C | 29.21 mm |
| October | 0.6 °C | 13.5 °C | 35.56 mm |
| November | -3.3 °C | 5.4 °C | 35.05 mm |
| December | -6.4 °C | 0.8 °C | 26.67 mm |
| Annual | 1 °C | 13.7 °C | 401.82 mm |
| 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 : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |