By late Saturday into Sunday, the pattern shifts to a Santa Ana (north easterly winds).
Strong winds Saturday, gusting to near 40 miles per hour, combined with very low humidity will create very risky fire conditions, especially across northwestern Oklahoma.
The forecast for areas above 1,000 feet is for winds of 15 mph to 30 mph and gusts up to 50 mph.
The humidity will drop into the 10-to-15 percent range at midday on Sunday, when the chance of wildfires will be greatest.
With the warning in place, Marin County Fire Department Chief Jason Weber has indefinitely suspended open burning within the county's borders. Flames burned less than one acre before Cal Fire put it out. To the public, a Red Flag Warning means high fire danger with increased probability of a quickly spreading vegetation fire in the area within 24 hours.
A separate but less imminent forecast may include a fire weather watch, which is issued to alert fire and land management agencies to the possibility that Red Flag conditions may exist beyond the first forecast period (12 hours).
In Ventura and Santa Barbara counties, the almost 250,000-acre Thomas Fire has burned since December 4.
Winter fire weather warnings are unusual but not unprecedented in the Bay Area.
Temperatures on Saturday are expected to be warmer, reaching into the low 60s, according to the National Weather Service.