Hillsboro, Wisconsin has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.4 °C (low) to 13 °C (high). Annual precipitation averages 938.5 Millimeters. Hillsboro 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 | -13.6 °C | -3.7 °C | 32.77 mm |
| February | -12.1 °C | -1.1 °C | 29.97 mm |
| March | -5.8 °C | 5.7 °C | 49.02 mm |
| April | 0.8 °C | 13.3 °C | 100.33 mm |
| May | 7.3 °C | 19.9 °C | 117.6 mm |
| June | 13 °C | 25.1 °C | 139.45 mm |
| July | 15.2 °C | 27.4 °C | 104.39 mm |
| August | 13.8 °C | 26.2 °C | 111.51 mm |
| September | 9.2 °C | 22.2 °C | 94.23 mm |
| October | 2.7 °C | 15 °C | 70.36 mm |
| November | -3.5 °C | 6.5 °C | 50.04 mm |
| December | -9.7 °C | -0.6 °C | 38.86 mm |
| Annual | 1.4 °C | 13 °C | 938.53 mm |
| 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 : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |