Here in Lake Havasu City, AZ, there are three seasons:
Summer lasts from the end of Spring Break until Snowbird Season in September/October. Snowbird Season lasts for months until March/April when Spring Break season starts. Spring Break lasts for a few months until the end of May/beginning of June when the Summer heat returns, driving away all of the Spring Breakers smart enough to get out.
Each change of season is indicated by the large group of people leaving or returning. Snowbirds arrive when it starts to get tolerable outside, but they're driven away like magnetic polar opposites when the Spring Breakers start showing up. And most of the Spring Breakers know better than to stick around when it starts hitting 110+ for Summer.