Mettawa, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.3 °C (low) to 14.5 °C (high). Annual precipitation averages 972.1 Millimeters. Mettawa 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 | -8.5 °C | -0.6 °C | 51.56 mm |
| February | -6.9 °C | 1.4 °C | 51.31 mm |
| March | -1.9 °C | 7.2 °C | 58.42 mm |
| April | 3.8 °C | 13.7 °C | 98.3 mm |
| May | 9.7 °C | 20 °C | 112.27 mm |
| June | 15.3 °C | 25.7 °C | 113.03 mm |
| July | 18.4 °C | 28.2 °C | 98.04 mm |
| August | 17.8 °C | 27.3 °C | 98.04 mm |
| September | 13.4 °C | 23.6 °C | 91.69 mm |
| October | 6.8 °C | 16.7 °C | 83.82 mm |
| November | 0.4 °C | 8.8 °C | 61.98 mm |
| December | -5.1 °C | 2.4 °C | 53.59 mm |
| Annual | 5.3 °C | 14.5 °C | 972.05 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |