Belfry, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.3 °C (low) to 15.6 °C (high). Annual precipitation averages 257.8 Millimeters. Belfry 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 | -11.5 °C | 2.7 °C | 8.13 mm |
| February | -9.9 °C | 4.3 °C | 7.62 mm |
| March | -5.1 °C | 10.5 °C | 13.21 mm |
| April | -0.8 °C | 14.7 °C | 24.13 mm |
| May | 4.4 °C | 19.6 °C | 48.51 mm |
| June | 8.9 °C | 25.3 °C | 46.23 mm |
| July | 12.2 °C | 30.5 °C | 21.84 mm |
| August | 10.8 °C | 29.8 °C | 16.76 mm |
| September | 5.8 °C | 23.7 °C | 25.4 mm |
| October | -0.7 °C | 15.7 °C | 24.38 mm |
| November | -6.2 °C | 8.1 °C | 11.68 mm |
| December | -11.2 °C | 2.7 °C | 9.91 mm |
| Annual | -0.3 °C | 15.6 °C | 257.8 mm |
| 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 : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |