Chelsea, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 30.6 °F (low) to 51.2 °F (high). Annual precipitation averages 33 Inches. Chelsea 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.1 °F | 21.0 °F | 1.12 in. |
| February | 3.7 °F | 25.7 °F | 1.04 in. |
| March | 15.4 °F | 37.5 °F | 1.64 in. |
| April | 28.9 °F | 51.3 °F | 2.88 in. |
| May | 41.8 °F | 64.7 °F | 3.7 in. |
| June | 51.9 °F | 73.7 °F | 4.61 in. |
| July | 55.9 °F | 77.8 °F | 3.82 in. |
| August | 53.7 °F | 75.8 °F | 3.97 in. |
| September | 46.0 °F | 68.2 °F | 3.8 in. |
| October | 34.1 °F | 54.2 °F | 3.11 in. |
| November | 23.0 °F | 38.7 °F | 1.87 in. |
| December | 10.1 °F | 26.1 °F | 1.44 in. |
| Annual | 30.6 °F | 51.2 °F | 33 in. |
| 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 4a : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |