https://www.mercurynews.com/2020/09/23/developing-heat-wave-expected-to-cook-bay-area-this-weekend/

Barometric pressure is beginning to build from southern California and is spreading north. Wind gusts will start to increase, especially at night, further drying out forest vegetation. Temperature gauges will be moving upward rapidly.

In short, the prime elements of the fall fire season will arrive by this weekend, according to the National Weather Service, and they will generate a heat wave that may last several days.