Belknap, Montana has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 1.6 °C (low) to 15.2 °C (high). Annual precipitation averages 577.6 Millimeters. Belknap is located in USDA Plant Hardiness Zone 6b. 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 | -5.2 °C | 1.8 °C | 62.23 mm |
| February | -4.8 °C | 4.8 °C | 50.29 mm |
| March | -2.5 °C | 9.6 °C | 52.07 mm |
| April | 0.4 °C | 14.7 °C | 42.93 mm |
| May | 4.1 °C | 20.5 °C | 53.59 mm |
| June | 7.7 °C | 24 °C | 57.15 mm |
| July | 9.9 °C | 30.3 °C | 23.11 mm |
| August | 9.4 °C | 30.6 °C | 20.83 mm |
| September | 5.6 °C | 24.4 °C | 24.64 mm |
| October | 1.3 °C | 14.9 °C | 54.1 mm |
| November | -2.1 °C | 5.8 °C | 70.87 mm |
| December | -5.1 °C | 1.3 °C | 65.79 mm |
| Annual | 1.6 °C | 15.2 °C | 577.6 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |