Boneau, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -1.1 °C (low) to 13.3 °C (high). Annual precipitation averages 364.2 Millimeters. Boneau is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.4 °C | -0.2 °C | 13.97 mm |
| February | -11.3 °C | 1.4 °C | 10.92 mm |
| March | -6.8 °C | 6.6 °C | 12.95 mm |
| April | -1.7 °C | 12.7 °C | 30.73 mm |
| May | 3.3 °C | 18.1 °C | 56.9 mm |
| June | 7.7 °C | 22.6 °C | 84.33 mm |
| July | 10.7 °C | 28.7 °C | 37.59 mm |
| August | 9.6 °C | 27.9 °C | 28.7 mm |
| September | 5.1 °C | 21.7 °C | 34.04 mm |
| October | -0.9 °C | 13.7 °C | 24.64 mm |
| November | -6.2 °C | 5.9 °C | 18.29 mm |
| December | -10.8 °C | 0.8 °C | 11.18 mm |
| Annual | -1.1 °C | 13.3 °C | 364.24 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 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 |