According to the 2023 USDA Hardiness Zone Map St. Lawrence County, New York is in Zones 4a (-30°F to -25°F), 4b (-25°F to -20°F), 5a (-20°F to -15°F) and 5b (-15°F to -10°F). This is a change from the 2012 USDA Hardiness Zone Map which has St. Lawrence County in Zones 3b (-35°F to -30°F), 4a (-30°F to -25°F) and 4b (-25°F to -20°F).