Warren, 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 979.4 Millimeters. Warren 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 | -11.6 °C | -2.7 °C | 35.56 mm |
| February | -9.7 °C | -0.3 °C | 40.13 mm |
| March | -3.7 °C | 6.6 °C | 54.61 mm |
| April | 2.4 °C | 14.3 °C | 98.55 mm |
| May | 9 °C | 20.8 °C | 109.98 mm |
| June | 14.6 °C | 25.9 °C | 144.02 mm |
| July | 16.5 °C | 27.6 °C | 116.59 mm |
| August | 15.3 °C | 26.7 °C | 105.16 mm |
| September | 10.7 °C | 23.2 °C | 93.22 mm |
| October | 4.3 °C | 16.1 °C | 75.18 mm |
| November | -1.8 °C | 7.6 °C | 61.21 mm |
| December | -7.9 °C | 0.4 °C | 45.21 mm |
| Annual | 3.2 °C | 13.9 °C | 979.42 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 |