The worst of California’s heat wave has arrived for the final day of Labor Day weekend celebrations, with temperatures expected to rise as high as 110 degrees in St. Helena and Healdsburg. The intense heat has prompted warnings about possible rolling blackouts Monday on California electric grid.
What’s behind the sizzling temperatures? It’s called a heat dome: an atmospheric lid is trapping hot air over the Western US, triggering intense heat. You can read more here about the science of California’s worsening heat waves, as explained by the Chronicle weather science team.