Early this morning, I welcomed the arrival of winter in the Santa Cruz Mountains, though your Hallmark calendar shows Fall only started a few weeks ago. Simple explanation. California only has two seasons: Summer and Winter. In the past, I lived in both New York and Michigan; states which actually have four seasons. How do you mark the passage from season to season in California? Rain. The end of winter is declared and back-dated when you realize it hasn't rained for 30 days. The start of winter is marked by the first rain. Pretty simple.