Sycamore, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.7 °F (low) to 58.2 °F (high). Annual precipitation averages 37.7 Inches. 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 | 13.2 °F | 28.9 °F | 1.74 in. |
| February | 16.5 °F | 33.2 °F | 1.74 in. |
| March | 26.5 °F | 45.3 °F | 2.27 in. |
| April | 37.0 °F | 58.7 °F | 3.54 in. |
| May | 48.6 °F | 70.2 °F | 4.89 in. |
| June | 58.6 °F | 79.8 °F | 4.64 in. |
| July | 62.5 °F | 82.9 °F | 3.89 in. |
| August | 60.4 °F | 81.1 °F | 4.03 in. |
| September | 52.1 °F | 75.1 °F | 3.43 in. |
| October | 40.4 °F | 62.3 °F | 3.01 in. |
| November | 29.7 °F | 47.1 °F | 2.46 in. |
| December | 19.2 °F | 34.3 °F | 2.01 in. |
| Annual | 38.7 °F | 58.2 °F | 37.65 in. |
| 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 : -15°F to -10°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 |