Casco, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.2 °C (low) to 11.7 °C (high). Annual precipitation averages 804.9 Millimeters. Casco is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.8 °C | -3.8 °C | 38.61 mm |
| February | -11 °C | -2.2 °C | 28.96 mm |
| March | -5.7 °C | 3.8 °C | 43.43 mm |
| April | 0.7 °C | 10.6 °C | 77.22 mm |
| May | 6.9 °C | 17.8 °C | 87.38 mm |
| June | 12.5 °C | 23.2 °C | 99.06 mm |
| July | 15.3 °C | 26.1 °C | 90.17 mm |
| August | 14.6 °C | 25.3 °C | 87.38 mm |
| September | 10.3 °C | 21.2 °C | 81.28 mm |
| October | 3.9 °C | 13.6 °C | 75.69 mm |
| November | -2 °C | 6 °C | 52.83 mm |
| December | -7.9 °C | -0.7 °C | 42.93 mm |
| Annual | 2.2 °C | 11.7 °C | 804.94 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |