Waukegan, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.2 °F (low) to 56.6 °F (high). Annual precipitation averages 36.6 Inches. Waukegan 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 | 16.7 °F | 30.8 °F | 2.09 in. |
| February | 19.3 °F | 33.9 °F | 2.06 in. |
| March | 28.1 °F | 43.4 °F | 2.09 in. |
| April | 38.2 °F | 54.1 °F | 3.73 in. |
| May | 48.2 °F | 65.1 °F | 4.35 in. |
| June | 58.2 °F | 75.1 °F | 4.23 in. |
| July | 64.6 °F | 80.4 °F | 3.62 in. |
| August | 64.1 °F | 79.2 °F | 3.62 in. |
| September | 56.4 °F | 72.7 °F | 3.14 in. |
| October | 44.5 °F | 60.9 °F | 3.16 in. |
| November | 33.0 °F | 47.7 °F | 2.42 in. |
| December | 22.6 °F | 36.0 °F | 2.05 in. |
| Annual | 41.2 °F | 56.6 °F | 36.56 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |