Hardin, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.7 °F (low) to 62.4 °F (high). Annual precipitation averages 13.1 Inches. Hardin 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 12.0 °F | 36.0 °F | 0.46 in. |
| February | 15.1 °F | 40.3 °F | 0.43 in. |
| March | 23.9 °F | 51.2 °F | 0.67 in. |
| April | 32.8 °F | 61.8 °F | 1.56 in. |
| May | 42.3 °F | 70.9 °F | 2.44 in. |
| June | 51.1 °F | 80.9 °F | 1.88 in. |
| July | 56.9 °F | 90.4 °F | 1.32 in. |
| August | 54.6 °F | 89.3 °F | 0.77 in. |
| September | 45.3 °F | 79.1 °F | 1.28 in. |
| October | 33.5 °F | 63.7 °F | 1.3 in. |
| November | 22.8 °F | 48.2 °F | 0.54 in. |
| December | 13.7 °F | 37.3 °F | 0.49 in. |
| Annual | 33.7 °F | 62.4 °F | 13.14 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 | Dfb - Humid Continental Mild Summer, Wet All Year |