Tonica, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 15.9 °C (high). Annual precipitation averages 931.2 Millimeters. Tonica is located in USDA Plant Hardiness Zone 5b. 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 | -9.2 °C | -0.4 °C | 46.23 mm |
| February | -7.2 °C | 2.1 °C | 44.45 mm |
| March | -1.8 °C | 9 °C | 61.47 mm |
| April | 4 °C | 16.4 °C | 88.9 mm |
| May | 10.6 °C | 22.7 °C | 115.82 mm |
| June | 15.9 °C | 27.6 °C | 109.22 mm |
| July | 17.9 °C | 29.2 °C | 97.28 mm |
| August | 16.7 °C | 28.2 °C | 92.96 mm |
| September | 12.2 °C | 25.2 °C | 85.34 mm |
| October | 5.8 °C | 18.2 °C | 75.44 mm |
| November | -0.4 °C | 9.7 °C | 63.5 mm |
| December | -5.9 °C | 2.6 °C | 50.55 mm |
| Annual | 4.9 °C | 15.9 °C | 931.16 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 5b : -26.1°C to -23.3°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 |