Mellen, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.9 °C (low) to 10.4 °C (high). Annual precipitation averages 886.2 Millimeters. Mellen is located in USDA Plant Hardiness Zone 4a. 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 | -16.4 °C | -6.3 °C | 39.37 mm |
| February | -15.2 °C | -3.4 °C | 28.96 mm |
| March | -9.4 °C | 2.8 °C | 43.94 mm |
| April | -2.2 °C | 9.8 °C | 74.42 mm |
| May | 4.4 °C | 17.7 °C | 91.44 mm |
| June | 10.1 °C | 22.8 °C | 110.74 mm |
| July | 13.1 °C | 25.2 °C | 123.7 mm |
| August | 12 °C | 24.3 °C | 89.41 mm |
| September | 7.9 °C | 19.9 °C | 94.74 mm |
| October | 1.4 °C | 12.2 °C | 92.46 mm |
| November | -5.1 °C | 3.5 °C | 53.59 mm |
| December | -11.8 °C | -3.3 °C | 43.43 mm |
| Annual | -0.9 °C | 10.4 °C | 886.2 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 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |