Carthage, 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 62.2 °F (high). Annual precipitation averages 40.2 Inches. Carthage 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.4 °F | 33.3 °F | 1.78 in. |
| February | 20.0 °F | 38.1 °F | 1.96 in. |
| March | 30.2 °F | 50.5 °F | 2.53 in. |
| April | 41.1 °F | 63.4 °F | 4.06 in. |
| May | 52.7 °F | 73.6 °F | 5.34 in. |
| June | 62.5 °F | 82.8 °F | 4.92 in. |
| July | 65.9 °F | 86.4 °F | 4.15 in. |
| August | 63.7 °F | 84.7 °F | 3.9 in. |
| September | 55.2 °F | 78.8 °F | 3.74 in. |
| October | 43.5 °F | 65.9 °F | 3.23 in. |
| November | 32.0 °F | 51.0 °F | 2.67 in. |
| December | 22.1 °F | 38.4 °F | 1.96 in. |
| Annual | 42.1 °F | 62.2 °F | 40.24 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 |