Pontiac, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.9 °F (low) to 61.1 °F (high). Annual precipitation averages 37 Inches. Pontiac is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.2 °F | 32.0 °F | 2.03 in. |
| February | 19.4 °F | 36.5 °F | 1.78 in. |
| March | 29.0 °F | 48.9 °F | 2.56 in. |
| April | 39.5 °F | 62.5 °F | 3.48 in. |
| May | 51.1 °F | 73.5 °F | 4.47 in. |
| June | 60.7 °F | 81.9 °F | 3.94 in. |
| July | 64.1 °F | 84.6 °F | 3.97 in. |
| August | 61.9 °F | 82.9 °F | 3.56 in. |
| September | 53.6 °F | 77.9 °F | 3.25 in. |
| October | 42.3 °F | 65.2 °F | 3.24 in. |
| November | 31.6 °F | 49.9 °F | 2.65 in. |
| December | 21.8 °F | 37.1 °F | 2.08 in. |
| Annual | 40.9 °F | 61.1 °F | 37.01 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 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 |