Pontiac, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5 °C (low) to 16.1 °C (high). Annual precipitation averages 940.1 Millimeters. 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 | -8.8 °C | 0 °C | 51.56 mm |
| February | -7 °C | 2.5 °C | 45.21 mm |
| March | -1.7 °C | 9.4 °C | 65.02 mm |
| April | 4.2 °C | 16.9 °C | 88.39 mm |
| May | 10.6 °C | 23.1 °C | 113.54 mm |
| June | 15.9 °C | 27.7 °C | 100.08 mm |
| July | 17.8 °C | 29.2 °C | 100.84 mm |
| August | 16.6 °C | 28.3 °C | 90.42 mm |
| September | 12 °C | 25.5 °C | 82.55 mm |
| October | 5.7 °C | 18.4 °C | 82.3 mm |
| November | -0.2 °C | 9.9 °C | 67.31 mm |
| December | -5.7 °C | 2.8 °C | 52.83 mm |
| Annual | 5 °C | 16.1 °C | 940.05 mm |
| 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 : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |