Mattoon, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43.6 °F (low) to 63.3 °F (high). Annual precipitation averages 41.5 Inches. Mattoon 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 | 19.8 °F | 35.7 °F | 2.58 in. |
| February | 22.8 °F | 40.4 °F | 2.23 in. |
| March | 31.8 °F | 51.5 °F | 2.97 in. |
| April | 42.6 °F | 64.1 °F | 4.74 in. |
| May | 54.0 °F | 74.3 °F | 4.33 in. |
| June | 63.0 °F | 82.9 °F | 4.79 in. |
| July | 65.8 °F | 86.0 °F | 4.16 in. |
| August | 63.7 °F | 84.8 °F | 2.81 in. |
| September | 56.1 °F | 79.4 °F | 3.01 in. |
| October | 44.7 °F | 67.0 °F | 3.6 in. |
| November | 33.6 °F | 52.4 °F | 3.57 in. |
| December | 25.2 °F | 40.5 °F | 2.73 in. |
| Annual | 43.6 °F | 63.3 °F | 41.52 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 |