Dellwood, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.3 °C (low) to 13.4 °C (high). Annual precipitation averages 892.1 Millimeters. Dellwood is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14 °C | -3.5 °C | 30.99 mm |
| February | -12.3 °C | -0.8 °C | 29.21 mm |
| March | -6.2 °C | 5.9 °C | 45.21 mm |
| April | 0.5 °C | 13.7 °C | 87.88 mm |
| May | 7.4 °C | 20.7 °C | 105.92 mm |
| June | 13 °C | 25.9 °C | 128.02 mm |
| July | 15.2 °C | 28.1 °C | 114.81 mm |
| August | 13.8 °C | 26.8 °C | 106.43 mm |
| September | 9.3 °C | 22.7 °C | 89.92 mm |
| October | 2.7 °C | 15.2 °C | 68.07 mm |
| November | -3.7 °C | 6.6 °C | 46.74 mm |
| December | -9.8 °C | -0.6 °C | 38.86 mm |
| Annual | 1.3 °C | 13.4 °C | 892.06 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |