Where do monarch butterflies mainly overwinter in Mexico?

Monarch butterflies mainly overwinter in the mountains of central Mexico.

Eastern North American monarchs migrate thousands of kilometres south in autumn, gathering in high-elevation oyamel fir forests. The cool, moist conditions help them conserve energy during several months of winter dormancy.

These butterflies do not all complete the entire round trip themselves. The generation that travels to Mexico survives for months, then begins the northward journey and lays eggs. Several shorter-lived generations continue north before the autumn migration begins again.

This migration is often confused with the movements of western North American monarchs. Many western monarchs traditionally overwinter along the California coast, although some populations also move toward Mexico. The Mexican wintering colonies are a defining feature of the eastern migration.