Polson, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.5 °C (low) to 13.8 °C (high). Annual precipitation averages 412.8 Millimeters. 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 | -6.2 °C | 0.9 °C | 30.48 mm |
| February | -5.9 °C | 3.1 °C | 18.29 mm |
| March | -2.9 °C | 8.4 °C | 29.72 mm |
| April | 0.6 °C | 13.4 °C | 41.4 mm |
| May | 4.5 °C | 18.7 °C | 49.28 mm |
| June | 8.2 °C | 22.3 °C | 60.96 mm |
| July | 10.9 °C | 28.6 °C | 24.13 mm |
| August | 10.2 °C | 28.5 °C | 18.29 mm |
| September | 6.2 °C | 22.3 °C | 31.5 mm |
| October | 1.2 °C | 13.5 °C | 41.91 mm |
| November | -2.8 °C | 5.5 °C | 33.02 mm |
| December | -5.9 °C | 0.9 °C | 33.78 mm |
| Annual | 1.5 °C | 13.8 °C | 412.76 mm |
| 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 : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |