California’s worst heat wave has arrived on the final day of Labor Day weekend celebrations, with temperatures expected to reach 110 degrees in St. Helena and Healdsburg. It has triggered extreme heat warnings California power grid could experience outages Monday.
What is behind extreme temperatures? It’s called a heat dome: an atmospheric cover that traps warm air over the western U.S., triggering intense heat. Read more about the science here California’s heat waves are getting worseThe Chronicle’s meteorological science team explained.