Chelsea, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.8 °C (low) to 10.7 °C (high). Annual precipitation averages 838.2 Millimeters. 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 | -16.6 °C | -6.1 °C | 28.45 mm |
| February | -15.7 °C | -3.5 °C | 26.42 mm |
| March | -9.2 °C | 3.1 °C | 41.66 mm |
| April | -1.7 °C | 10.7 °C | 73.15 mm |
| May | 5.4 °C | 18.2 °C | 93.98 mm |
| June | 11.1 °C | 23.2 °C | 117.09 mm |
| July | 13.3 °C | 25.4 °C | 97.03 mm |
| August | 12.1 °C | 24.3 °C | 100.84 mm |
| September | 7.8 °C | 20.1 °C | 96.52 mm |
| October | 1.2 °C | 12.3 °C | 78.99 mm |
| November | -5 °C | 3.7 °C | 47.5 mm |
| December | -12.2 °C | -3.3 °C | 36.58 mm |
| Annual | -0.8 °C | 10.7 °C | 838.21 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 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |