According to the 2023 USDA Hardiness Zone Map Harper County, Kansas is in Zones 6b (-5°F to 0°F) and 7a (0°F to 5°F). There is no change from the 2012 USDA Hardiness Zone Map which has Harper County in also in Zones 6b (-5°F to 0°F) and 7a (0°F to 5°F).