Eastern monarchs travel from southern Canada and the northeast United States all the way to central Mexico, where they cluster in mountain forests at high elevations. These monarch overwintering sites provide the cool, moist climate monarchs need to survive the winter. AdvertisementWestern monarchs, meanwhile, migrate to coastal California—especially southern California—to find their own overwintering habitat. In early March, as weather warms, the overwintering monarchs begin their spring migration northward. They reach breeding grounds in the central United States, where they lay their eggs and die.