Fort Benton, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -0.3 °C (low) to 15.3 °C (high). Annual precipitation averages 337.3 Millimeters. Fort Benton is located in USDA Plant Hardiness Zone 4a. 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 | -12.2 °C | 1.7 °C | 12.95 mm |
| February | -10.8 °C | 3.9 °C | 11.18 mm |
| March | -6.3 °C | 8.8 °C | 13.21 mm |
| April | -0.3 °C | 15.1 °C | 37.85 mm |
| May | 4.8 °C | 19.7 °C | 54.1 mm |
| June | 9.3 °C | 24.4 °C | 65.53 mm |
| July | 12.2 °C | 30.1 °C | 31.75 mm |
| August | 10.9 °C | 29.8 °C | 30.23 mm |
| September | 5.9 °C | 23.9 °C | 29.97 mm |
| October | -0.7 °C | 15.8 °C | 23.37 mm |
| November | -6.2 °C | 8.1 °C | 14.99 mm |
| December | -10.7 °C | 2.6 °C | 12.19 mm |
| Annual | -0.3 °C | 15.3 °C | 337.32 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 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |