Thornton, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.9 °F (low) to 54.6 °F (high). Annual precipitation averages 33.1 Inches. Thornton is located in USDA Plant Hardiness Zone 5a. 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 | 7.3 °F | 24.7 °F | 1.28 in. |
| February | 8.9 °F | 28.8 °F | 1.09 in. |
| March | 19.8 °F | 40.5 °F | 1.79 in. |
| April | 32.1 °F | 54.5 °F | 3.05 in. |
| May | 44.3 °F | 67.4 °F | 3.76 in. |
| June | 54.3 °F | 76.9 °F | 4.42 in. |
| July | 58.4 °F | 81.1 °F | 3.87 in. |
| August | 56.4 °F | 79.2 °F | 3.65 in. |
| September | 48.1 °F | 71.5 °F | 3.63 in. |
| October | 36.6 °F | 57.7 °F | 3.0 in. |
| November | 25.9 °F | 42.8 °F | 1.96 in. |
| December | 14.4 °F | 29.8 °F | 1.6 in. |
| Annual | 33.9 °F | 54.6 °F | 33.1 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 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |