Polson, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.7 °F (low) to 56.9 °F (high). Annual precipitation averages 16.3 Inches. Polson is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 20.8 °F | 33.7 °F | 1.2 in. |
| February | 21.3 °F | 37.6 °F | 0.72 in. |
| March | 26.8 °F | 47.1 °F | 1.17 in. |
| April | 33.1 °F | 56.2 °F | 1.63 in. |
| May | 40.1 °F | 65.7 °F | 1.94 in. |
| June | 46.7 °F | 72.2 °F | 2.4 in. |
| July | 51.7 °F | 83.4 °F | 0.95 in. |
| August | 50.4 °F | 83.3 °F | 0.72 in. |
| September | 43.2 °F | 72.2 °F | 1.24 in. |
| October | 34.1 °F | 56.3 °F | 1.65 in. |
| November | 26.9 °F | 41.9 °F | 1.3 in. |
| December | 21.3 °F | 33.7 °F | 1.33 in. |
| Annual | 34.7 °F | 56.9 °F | 16.25 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |