Highland Park, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6 °C (low) to 14.5 °C (high). Annual precipitation averages 982.5 Millimeters. Highland Park 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.7 °C | -0.3 °C | 53.34 mm |
| February | -6.2 °C | 1.7 °C | 50.8 mm |
| March | -1.3 °C | 7.1 °C | 56.13 mm |
| April | 4.2 °C | 13.3 °C | 97.54 mm |
| May | 9.9 °C | 19.8 °C | 117.35 mm |
| June | 15.6 °C | 25.5 °C | 108.2 mm |
| July | 19.1 °C | 28.2 °C | 95 mm |
| August | 18.8 °C | 27.3 °C | 102.62 mm |
| September | 14.4 °C | 23.6 °C | 91.19 mm |
| October | 7.8 °C | 16.7 °C | 87.88 mm |
| November | 1.3 °C | 8.9 °C | 66.29 mm |
| December | -4.3 °C | 2.6 °C | 56.13 mm |
| Annual | 6 °C | 14.5 °C | 982.47 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 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 |