Naperville, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.5 °C (low) to 15.5 °C (high). Annual precipitation averages 1006.6 Millimeters. Naperville is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.2 °C | -0.3 °C | 52.58 mm |
| February | -7.7 °C | 1.8 °C | 51.31 mm |
| March | -2.4 °C | 8.4 °C | 60.71 mm |
| April | 3.4 °C | 15.6 °C | 100.33 mm |
| May | 9.5 °C | 21.8 °C | 124.46 mm |
| June | 15.1 °C | 27.2 °C | 116.33 mm |
| July | 17.6 °C | 29.3 °C | 100.08 mm |
| August | 16.7 °C | 28.3 °C | 104.14 mm |
| September | 12.3 °C | 24.8 °C | 83.31 mm |
| October | 5.6 °C | 17.5 °C | 91.19 mm |
| November | -0.6 °C | 9.3 °C | 65.53 mm |
| December | -5.9 °C | 2.5 °C | 56.64 mm |
| Annual | 4.5 °C | 15.5 °C | 1006.61 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°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 |