Modesto, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43.9 °F (low) to 63.6 °F (high). Annual precipitation averages 39.7 Inches. Modesto 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 | 19.9 °F | 35.7 °F | 2.21 in. |
| February | 23.3 °F | 40.9 °F | 2.01 in. |
| March | 32.4 °F | 52.1 °F | 2.88 in. |
| April | 42.9 °F | 64.8 °F | 4.37 in. |
| May | 54.4 °F | 74.7 °F | 4.8 in. |
| June | 63.5 °F | 83.1 °F | 4.5 in. |
| July | 66.6 °F | 86.1 °F | 3.69 in. |
| August | 64.4 °F | 85.0 °F | 3.32 in. |
| September | 56.0 °F | 79.7 °F | 3.29 in. |
| October | 44.7 °F | 67.4 °F | 3.2 in. |
| November | 34.1 °F | 52.4 °F | 3.16 in. |
| December | 25.1 °F | 40.7 °F | 2.27 in. |
| Annual | 43.9 °F | 63.6 °F | 39.7 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 |