Great Falls, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 1 °C (low) to 14.6 °C (high). Annual precipitation averages 369.8 Millimeters. Great Falls is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.9 °C | 2.3 °C | 15.49 mm |
| February | -8.6 °C | 3.5 °C | 14.48 mm |
| March | -4.7 °C | 8.2 °C | 16.76 mm |
| April | 0 °C | 13.3 °C | 42.67 mm |
| May | 4.9 °C | 18.6 °C | 55.63 mm |
| June | 9.2 °C | 23.2 °C | 68.83 mm |
| July | 12.3 °C | 29.3 °C | 30.73 mm |
| August | 11.5 °C | 28.9 °C | 28.19 mm |
| September | 7.1 °C | 22.8 °C | 33.02 mm |
| October | 1.3 °C | 14.9 °C | 28.96 mm |
| November | -3.7 °C | 7.7 °C | 20.07 mm |
| December | -7.9 °C | 2.8 °C | 14.99 mm |
| Annual | 1 °C | 14.6 °C | 369.82 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |