Big Sandy, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 30.6 °F (low) to 58 °F (high). Annual precipitation averages 12.7 Inches. Big Sandy 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 | 7.8 °F | 30.9 °F | 0.48 in. |
| February | 10.5 °F | 35.0 °F | 0.38 in. |
| March | 20.0 °F | 45.2 °F | 0.49 in. |
| April | 30.6 °F | 58.3 °F | 1.16 in. |
| May | 40.1 °F | 67.5 °F | 1.81 in. |
| June | 48.5 °F | 75.7 °F | 2.94 in. |
| July | 53.7 °F | 86.1 °F | 1.43 in. |
| August | 51.7 °F | 85.7 °F | 1.01 in. |
| September | 42.5 °F | 74.6 °F | 1.04 in. |
| October | 30.9 °F | 59.5 °F | 0.88 in. |
| November | 19.7 °F | 43.6 °F | 0.59 in. |
| December | 10.6 °F | 33.4 °F | 0.44 in. |
| Annual | 30.6 °F | 58 °F | 12.65 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 |