Sycamore, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 14.6 °C (high). Annual precipitation averages 956.3 Millimeters. Sycamore is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.4 °C | -1.7 °C | 44.2 mm |
| February | -8.6 °C | 0.7 °C | 44.2 mm |
| March | -3.1 °C | 7.4 °C | 57.66 mm |
| April | 2.8 °C | 14.8 °C | 89.92 mm |
| May | 9.2 °C | 21.2 °C | 124.21 mm |
| June | 14.8 °C | 26.6 °C | 117.86 mm |
| July | 16.9 °C | 28.3 °C | 98.81 mm |
| August | 15.8 °C | 27.3 °C | 102.36 mm |
| September | 11.2 °C | 23.9 °C | 87.12 mm |
| October | 4.7 °C | 16.8 °C | 76.45 mm |
| November | -1.3 °C | 8.4 °C | 62.48 mm |
| December | -7.1 °C | 1.3 °C | 51.05 mm |
| Annual | 3.7 °C | 14.6 °C | 956.32 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 |