Zortman, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 32 °F (low) to 54.1 °F (high). Annual precipitation averages 20 Inches. Zortman is located in USDA Plant Hardiness Zone 4b. 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 | 13.7 °F | 33.2 °F | 0.7 in. |
| February | 14.0 °F | 34.4 °F | 0.66 in. |
| March | 21.2 °F | 42.0 °F | 0.87 in. |
| April | 29.3 °F | 51.3 °F | 1.82 in. |
| May | 38.5 °F | 60.6 °F | 3.3 in. |
| June | 47.1 °F | 69.7 °F | 4.37 in. |
| July | 53.4 °F | 80.1 °F | 1.85 in. |
| August | 52.4 °F | 79.6 °F | 1.78 in. |
| September | 43.4 °F | 68.2 °F | 1.76 in. |
| October | 32.2 °F | 54.0 °F | 1.4 in. |
| November | 23.1 °F | 42.3 °F | 0.83 in. |
| December | 15.3 °F | 34.3 °F | 0.69 in. |
| Annual | 32 °F | 54.1 °F | 20.03 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 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |