Bynum, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 30.5 °F (low) to 55.5 °F (high). Annual precipitation averages 13.2 Inches. Bynum 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 | 13.3 °F | 35.2 °F | 0.41 in. |
| February | 14.0 °F | 36.6 °F | 0.46 in. |
| March | 20.7 °F | 43.9 °F | 0.63 in. |
| April | 28.7 °F | 52.7 °F | 1.47 in. |
| May | 37.3 °F | 62.3 °F | 2.19 in. |
| June | 44.6 °F | 69.8 °F | 2.68 in. |
| July | 50.2 °F | 80.4 °F | 1.1 in. |
| August | 48.6 °F | 79.7 °F | 1.14 in. |
| September | 41.0 °F | 69.5 °F | 1.25 in. |
| October | 31.2 °F | 56.4 °F | 0.87 in. |
| November | 22.0 °F | 43.4 °F | 0.54 in. |
| December | 14.7 °F | 35.7 °F | 0.44 in. |
| Annual | 30.5 °F | 55.5 °F | 13.18 in. |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 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 |