Oak Lawn, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.9 °C (low) to 15.5 °C (high). Annual precipitation averages 1007.4 Millimeters. Oak Lawn is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.8 °C | 0 °C | 54.86 mm |
| February | -6.3 °C | 2.1 °C | 52.07 mm |
| March | -1.1 °C | 8.1 °C | 60.45 mm |
| April | 4.6 °C | 15.3 °C | 100.33 mm |
| May | 10.7 °C | 21.4 °C | 120.14 mm |
| June | 16.3 °C | 27 °C | 109.47 mm |
| July | 19.1 °C | 29.4 °C | 110.74 mm |
| August | 18.2 °C | 28.3 °C | 106.17 mm |
| September | 13.9 °C | 24.8 °C | 81.53 mm |
| October | 7.1 °C | 17.5 °C | 87.38 mm |
| November | 0.9 °C | 9.5 °C | 64.77 mm |
| December | -4.7 °C | 2.9 °C | 59.44 mm |
| Annual | 5.9 °C | 15.5 °C | 1007.35 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |