Sun River, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 32.6 °F (low) to 58.5 °F (high). Annual precipitation averages 12.9 Inches. Sun River 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.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.8 °F | 36.5 °F | 0.38 in. |
| February | 15.9 °F | 38.7 °F | 0.47 in. |
| March | 22.4 °F | 46.8 °F | 0.56 in. |
| April | 30.8 °F | 56.7 °F | 1.54 in. |
| May | 39.4 °F | 65.9 °F | 2.03 in. |
| June | 47.0 °F | 73.7 °F | 2.73 in. |
| July | 52.0 °F | 84.7 °F | 1.1 in. |
| August | 50.5 °F | 83.7 °F | 1.11 in. |
| September | 43.1 °F | 73.2 °F | 1.17 in. |
| October | 33.8 °F | 59.3 °F | 0.86 in. |
| November | 24.2 °F | 45.6 °F | 0.54 in. |
| December | 16.7 °F | 37.0 °F | 0.38 in. |
| Annual | 32.6 °F | 58.5 °F | 12.87 in. |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 11 - May 20 |
| 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 |