Stockton, Illinois has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.2 °C (low) to 13.9 °C (high). Annual precipitation averages 963.4 Millimeters. Stockton is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.3 °C | -2.6 °C | 33.78 mm |
| February | -9.4 °C | -0.2 °C | 39.88 mm |
| March | -3.6 °C | 6.8 °C | 53.59 mm |
| April | 2.4 °C | 14.4 °C | 97.54 mm |
| May | 9 °C | 20.9 °C | 108.46 mm |
| June | 14.6 °C | 25.9 °C | 143.76 mm |
| July | 16.3 °C | 27.6 °C | 116.08 mm |
| August | 15.2 °C | 26.6 °C | 102.11 mm |
| September | 10.6 °C | 23.3 °C | 90.68 mm |
| October | 4.3 °C | 16.2 °C | 73.41 mm |
| November | -1.8 °C | 7.6 °C | 59.69 mm |
| December | -7.8 °C | 0.4 °C | 44.45 mm |
| Annual | 3.2 °C | 13.9 °C | 963.43 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |