According to the 2023 USDA Hardiness Zone Map Polk County, Minnesota is in Zones 3b (-35°F to -30°F) and 4a (-30°F to -25°F). This is a change from the 2012 USDA Hardiness Zone Map which has Polk County in Zones 3a (-40°F to -35°F), 3b (-35°F to -30°F) and 4a (-30°F to -25°F).