Pontoosuc, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43 °F (low) to 61.8 °F (high). Annual precipitation averages 40.1 Inches. Pontoosuc 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 | 17.0 °F | 33.1 °F | 1.71 in. |
| February | 20.8 °F | 37.7 °F | 1.97 in. |
| March | 31.0 °F | 49.9 °F | 2.62 in. |
| April | 42.0 °F | 62.7 °F | 3.94 in. |
| May | 53.6 °F | 73.0 °F | 5.29 in. |
| June | 63.4 °F | 82.2 °F | 4.99 in. |
| July | 67.0 °F | 85.8 °F | 4.16 in. |
| August | 64.8 °F | 84.4 °F | 3.87 in. |
| September | 56.3 °F | 78.1 °F | 3.81 in. |
| October | 44.6 °F | 65.4 °F | 3.17 in. |
| November | 33.0 °F | 50.6 °F | 2.59 in. |
| December | 22.9 °F | 38.1 °F | 2.01 in. |
| Annual | 43 °F | 61.8 °F | 40.13 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 |