Hartford, Wisconsin has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.1 °C (low) to 12.8 °C (high). Annual precipitation averages 890.5 Millimeters. Hartford is located in USDA Plant Hardiness Zone 5a. 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 | -12.2 °C | -3.2 °C | 41.66 mm |
| February | -10.7 °C | -1.2 °C | 37.08 mm |
| March | -5.1 °C | 5.3 °C | 49.02 mm |
| April | 1.1 °C | 12.5 °C | 91.69 mm |
| May | 7.3 °C | 19.2 °C | 101.09 mm |
| June | 12.8 °C | 24.6 °C | 115.06 mm |
| July | 15.3 °C | 27 °C | 102.36 mm |
| August | 14.3 °C | 25.9 °C | 98.3 mm |
| September | 9.8 °C | 22.2 °C | 80.77 mm |
| October | 3.6 °C | 14.9 °C | 74.17 mm |
| November | -2.5 °C | 6.9 °C | 52.07 mm |
| December | -8.3 °C | -0.1 °C | 47.24 mm |
| Annual | 2.1 °C | 12.8 °C | 890.51 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |