Dellwood, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.4 °F (low) to 56.1 °F (high). Annual precipitation averages 35.1 Inches. 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 | 6.8 °F | 25.7 °F | 1.22 in. |
| February | 9.9 °F | 30.5 °F | 1.15 in. |
| March | 20.9 °F | 42.6 °F | 1.78 in. |
| April | 32.9 °F | 56.7 °F | 3.46 in. |
| May | 45.4 °F | 69.2 °F | 4.17 in. |
| June | 55.4 °F | 78.6 °F | 5.04 in. |
| July | 59.3 °F | 82.5 °F | 4.52 in. |
| August | 56.8 °F | 80.2 °F | 4.19 in. |
| September | 48.7 °F | 72.8 °F | 3.54 in. |
| October | 36.9 °F | 59.3 °F | 2.68 in. |
| November | 25.4 °F | 43.8 °F | 1.84 in. |
| December | 14.3 °F | 31.0 °F | 1.53 in. |
| Annual | 34.4 °F | 56.1 °F | 35.12 in. |
| 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 : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |