How many generations of Monarch Butterflies from Mexico to Pennsylvania?

Three to Four generations.

- The last generation of the previous year migrates south to winter. The migrating generation is the first generation of monarchs in the Spring to begin migrating North. They will mate, lay eggs, and die. Their eggs will start the cycle over again, hatching, growing, pupating, emerging, mating, laying eggs and dying, again living up to 8 weeks. Each of three to four generations over the summer lives the same kind of life.