Vernon Hills, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 14.6 °C (high). Annual precipitation averages 963.2 Millimeters. Vernon Hills 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 | -9.1 °C | -0.8 °C | 49.78 mm |
| February | -7.6 °C | 1.3 °C | 50.29 mm |
| March | -2.4 °C | 7.3 °C | 58.67 mm |
| April | 3.3 °C | 14.2 °C | 97.54 mm |
| May | 9.2 °C | 20.3 °C | 113.28 mm |
| June | 14.8 °C | 26.1 °C | 113.79 mm |
| July | 17.8 °C | 28.5 °C | 97.28 mm |
| August | 17.1 °C | 27.4 °C | 98.3 mm |
| September | 12.7 °C | 23.7 °C | 86.61 mm |
| October | 6.2 °C | 16.6 °C | 83.06 mm |
| November | -0.2 °C | 8.8 °C | 61.21 mm |
| December | -5.7 °C | 2.2 °C | 53.34 mm |
| Annual | 4.7 °C | 14.6 °C | 963.15 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |