Colby, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.2 °C (low) to 11.3 °C (high). Annual precipitation averages 848.4 Millimeters. Colby 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 | -15.5 °C | -5.7 °C | 26.42 mm |
| February | -14.3 °C | -3.1 °C | 26.16 mm |
| March | -7.7 °C | 3.7 °C | 42.67 mm |
| April | -0.4 °C | 11.6 °C | 74.17 mm |
| May | 6.6 °C | 18.7 °C | 95.5 mm |
| June | 12.1 °C | 23.7 °C | 124.46 mm |
| July | 14.2 °C | 26.2 °C | 96.52 mm |
| August | 12.9 °C | 25 °C | 106.17 mm |
| September | 8.4 °C | 20.8 °C | 97.03 mm |
| October | 1.9 °C | 13.2 °C | 74.68 mm |
| November | -4.3 °C | 4.6 °C | 47.5 mm |
| December | -11.2 °C | -2.7 °C | 37.08 mm |
| Annual | 0.2 °C | 11.3 °C | 848.36 mm |
| 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 : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |