https://www.mercurynews.com/2023/04/26/warming-bay-area-temperatures-bring-with-them-spare-the-air-alert/

The Bay Area’s first warm-up of 2023 began to build Wednesday, and like most warming trends, it’s creating dirty air.

Unlike most of them, this heat wave — if it can be considered that — will be the equivalent of dipping a foot in water and then quickly pulling it out.