Hartsburg, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.1 °F (low) to 62.6 °F (high). Annual precipitation averages 38.6 Inches. 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 | 17.5 °F | 34.1 °F | 2.19 in. |
| February | 20.9 °F | 38.9 °F | 1.95 in. |
| March | 30.3 °F | 50.8 °F | 2.6 in. |
| April | 40.9 °F | 63.9 °F | 3.74 in. |
| May | 52.6 °F | 74.3 °F | 4.44 in. |
| June | 62.1 °F | 83.0 °F | 4.45 in. |
| July | 64.9 °F | 85.8 °F | 4.13 in. |
| August | 62.7 °F | 84.2 °F | 3.57 in. |
| September | 54.6 °F | 79.3 °F | 3.27 in. |
| October | 42.9 °F | 66.5 °F | 3.15 in. |
| November | 32.1 °F | 51.5 °F | 2.81 in. |
| December | 23.1 °F | 39.2 °F | 2.25 in. |
| Annual | 42.1 °F | 62.6 °F | 38.55 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |