Each year there are four generations of Monarch Butterflies.
1. The first generation emerge in the early spring in March and April.
2. The second generation emerges in late spring in May and June.
3. The third generation emerge in summer in July and Augus.
4. The last and fourth generation of the year emerge in autumn in September and October.
It is the fourth and last generation of the year that migrate south. After their hibernation period in the warmer regions of California and Mexico, these same butterflies start migrating back north. They mate in southern parts of the U.S. where they lay their eggs and die. Their eggs hatch into the first generation of the year.
More about the generations of Monarch, see MONARCH BUTTERFLY: GENERATION CYCLE