According to the Köppen climate classification system, Isle Royale National Park has a mild summer Humid continental climate (Dfb). According to the United States Department of Agriculture, the Plant Hardiness zone is 4b at 1178 ft (359 m) elevation with an average annual extreme minimum temperature of -24.2 °F (-31.2 °C).
According to the Köppen climate classification system Isle Royale National Park has a mild summer Humid continental climate (Dfb) According to the United States Department of Agriculture the Plant Hardiness zone is 4b at 1178 ft (359 m) elevation with an average annual extreme minimum temperature of -242 °F (-312 °C)