LOS ANGELES — Southern California's autumn cool-down will be short-lived, giving way to a fall heat wave and the first Santa Ana winds of the season.
The National Weather Service says high pressure will build into the area on Thursday, strengthen Friday and peak on Saturday.
That will cause temperatures in the valleys to jump into the 90s and then into triple digits for three or four days. Coastal temperatures will range from the lower 80s at the beaches to lower 90s inland, and the warm airmass won't allow much overnight cooling.
Santa Anas are expected each morning but the weather service says it will be a weak event, with winds of just 15 mph to 25 mph. Forecasters say they'll keep a close eye on the winds in case they increase.