Hartsburg, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.6 °C (low) to 17 °C (high). Annual precipitation averages 979.2 Millimeters. Hartsburg is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.1 °C | 1.2 °C | 55.63 mm |
| February | -6.2 °C | 3.8 °C | 49.53 mm |
| March | -0.9 °C | 10.4 °C | 66.04 mm |
| April | 4.9 °C | 17.7 °C | 95 mm |
| May | 11.4 °C | 23.5 °C | 112.78 mm |
| June | 16.7 °C | 28.3 °C | 113.03 mm |
| July | 18.3 °C | 29.9 °C | 104.9 mm |
| August | 17.1 °C | 29 °C | 90.68 mm |
| September | 12.6 °C | 26.3 °C | 83.06 mm |
| October | 6.1 °C | 19.2 °C | 80.01 mm |
| November | 0.1 °C | 10.8 °C | 71.37 mm |
| December | -4.9 °C | 4 °C | 57.15 mm |
| Annual | 5.6 °C | 17 °C | 979.18 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |