Highland, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.6 °C (low) to 18.6 °C (high). Annual precipitation averages 1129.3 Millimeters. Highland is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.4 °C | 3.7 °C | 69.09 mm |
| February | -3.6 °C | 6.7 °C | 60.45 mm |
| March | 1.4 °C | 12.6 °C | 85.85 mm |
| April | 7.2 °C | 19.2 °C | 125.22 mm |
| May | 13.3 °C | 24.2 °C | 128.02 mm |
| June | 18.2 °C | 29.2 °C | 120.9 mm |
| July | 20.1 °C | 30.9 °C | 109.73 mm |
| August | 19 °C | 30.4 °C | 93.73 mm |
| September | 14.2 °C | 26.9 °C | 84.33 mm |
| October | 7.8 °C | 20.4 °C | 85.34 mm |
| November | 1.9 °C | 12.4 °C | 95 mm |
| December | -2.8 °C | 6.2 °C | 71.63 mm |
| Annual | 7.6 °C | 18.6 °C | 1129.29 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |