According to the 2023 USDA Hardiness Zone Map Hancock County, Illinois is in Zones 5b (-15°F to -10°F) and 6a (-10°F to -5°F). There is no change from the 2012 USDA Hardiness Zone Map which has Hancock County in also in Zones 5b (-15°F to -10°F) and 6a (-10°F to -5°F).