Harlowton, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 31.2 °F (low) to 57.8 °F (high). Annual precipitation averages 13.8 Inches. Harlowton is located in USDA Plant Hardiness Zone 4b. 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 | 14.8 °F | 36.5 °F | 0.32 in. |
| February | 15.0 °F | 38.7 °F | 0.38 in. |
| March | 21.8 °F | 47.2 °F | 0.57 in. |
| April | 28.9 °F | 55.2 °F | 1.57 in. |
| May | 37.5 °F | 64.2 °F | 2.56 in. |
| June | 45.6 °F | 73.2 °F | 2.76 in. |
| July | 51.2 °F | 84.0 °F | 1.53 in. |
| August | 49.2 °F | 83.0 °F | 1.2 in. |
| September | 41.2 °F | 72.6 °F | 1.17 in. |
| October | 31.2 °F | 58.4 °F | 0.83 in. |
| November | 22.2 °F | 44.9 °F | 0.49 in. |
| December | 15.7 °F | 36.2 °F | 0.46 in. |
| Annual | 31.2 °F | 57.8 °F | 13.84 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 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |