Poplar Grove, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.4 °C (low) to 14.3 °C (high). Annual precipitation averages 961.9 Millimeters. Poplar Grove 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 | -10.6 °C | -1.8 °C | 41.91 mm |
| February | -8.9 °C | 0.4 °C | 41.66 mm |
| March | -3.6 °C | 7.1 °C | 54.61 mm |
| April | 2.3 °C | 14.3 °C | 93.98 mm |
| May | 8.7 °C | 20.7 °C | 112.52 mm |
| June | 14.2 °C | 26.1 °C | 137.41 mm |
| July | 16.4 °C | 28.1 °C | 98.81 mm |
| August | 15.4 °C | 27.2 °C | 104.9 mm |
| September | 11 °C | 23.6 °C | 92.2 mm |
| October | 4.6 °C | 16.3 °C | 73.41 mm |
| November | -1.4 °C | 8.1 °C | 59.94 mm |
| December | -7.3 °C | 1.1 °C | 50.55 mm |
| Annual | 3.4 °C | 14.3 °C | 961.9 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |