Hardin, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 44.7 °F (low) to 65.3 °F (high). Annual precipitation averages 42.6 Inches. Hardin is located in USDA Plant Hardiness Zone 6b. 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 | 21.0 °F | 38.3 °F | 2.55 in. |
| February | 24.2 °F | 43.6 °F | 2.48 in. |
| March | 33.2 °F | 54.5 °F | 3.32 in. |
| April | 43.8 °F | 66.6 °F | 4.46 in. |
| May | 55.0 °F | 75.7 °F | 5.04 in. |
| June | 64.0 °F | 84.3 °F | 4.48 in. |
| July | 67.4 °F | 87.6 °F | 3.97 in. |
| August | 65.4 °F | 86.7 °F | 3.46 in. |
| September | 56.7 °F | 80.2 °F | 3.45 in. |
| October | 45.4 °F | 68.4 °F | 3.22 in. |
| November | 34.6 °F | 54.4 °F | 3.48 in. |
| December | 25.6 °F | 42.8 °F | 2.68 in. |
| Annual | 44.7 °F | 65.3 °F | 42.59 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 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |