Boneau, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 30 °F (low) to 56 °F (high). Annual precipitation averages 14.3 Inches. 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 | 9.7 °F | 31.7 °F | 0.55 in. |
| February | 11.6 °F | 34.5 °F | 0.43 in. |
| March | 19.7 °F | 43.8 °F | 0.51 in. |
| April | 29.0 °F | 54.8 °F | 1.21 in. |
| May | 38.0 °F | 64.6 °F | 2.24 in. |
| June | 45.8 °F | 72.7 °F | 3.32 in. |
| July | 51.3 °F | 83.6 °F | 1.48 in. |
| August | 49.3 °F | 82.2 °F | 1.13 in. |
| September | 41.2 °F | 71.1 °F | 1.34 in. |
| October | 30.4 °F | 56.6 °F | 0.97 in. |
| November | 20.8 °F | 42.7 °F | 0.72 in. |
| December | 12.6 °F | 33.4 °F | 0.44 in. |
| Annual | 30 °F | 56 °F | 14.34 in. |
| 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 : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |