Libby, Montana has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.2 °C (low) to 14.9 °C (high). Annual precipitation averages 439.7 Millimeters. Libby is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.9 °C | 0.7 °C | 44.7 mm |
| February | -5.5 °C | 4.2 °C | 30.73 mm |
| March | -3 °C | 9.7 °C | 44.96 mm |
| April | -0.2 °C | 15.3 °C | 25.65 mm |
| May | 3.8 °C | 21 °C | 34.29 mm |
| June | 7.7 °C | 24.7 °C | 41.91 mm |
| July | 9.7 °C | 30.7 °C | 21.59 mm |
| August | 8.9 °C | 30.5 °C | 17.02 mm |
| September | 5.2 °C | 23.8 °C | 23.62 mm |
| October | 1.2 °C | 13.8 °C | 40.64 mm |
| November | -2.1 °C | 4.6 °C | 56.64 mm |
| December | -5.3 °C | 0.2 °C | 57.91 mm |
| Annual | 1.2 °C | 14.9 °C | 439.66 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |