NAPA COUNTY (CBS SF) – A Red Flag warning remains in effect Monday as crews battle fires in Wine Country, while the entire Bay Area deals with another day of hot temperatures during a late September heat wave.

The National Weather Service said the warning is in effect for the North Bay and East Bay hills above 1,000 feet through at least 9 p.m. Monday as a combination of strong winds, low humidity and high temperatures creates what forecasters described in a statement as “critical fire conditions.”

READ MORE: Man Found Shot Dead In East Oakland

Forecasters said winds in the North Bay hills ranged from 35 to 55 mph overnight, with some gusts exceeding 60 mph. The Weather Service said one of its weather stations located near the Mayacmas Mountains in northern Sonoma County reported a gust of 67 mph. Meanwhile, humidity levels dropped into the teens along the North and East Bay ridges.

READ MORE: Fremont Police Surround Home Following Shooting; 1 Injured

The challenging conditions for firefighters come as crews continue to battle the Glass, Shady and Boysen fires, which exploded in size overnight after being sparked over the weekend. The fires, which have since merged, have grown to 11,000 acres with zero containment. Numerous evacuations have been ordered in Sonoma and Napa counties, while  smoke from the fire has drifted over much of the Bay Area.

Along with the Red Flag Warning, a separate heat advisory remains in effect for nearly the entire Bay Area through 7 p.m. Monday, as areas along the Bay are expected to reach well into the 90s, while inland areas are expected to see temperatures above 100.

As of 9 a.m., temperatures were already surging into the 70s and 80s in much of the area, including 80 degrees at San Francisco International Airport, 81 in Oakland and 86 in Napa.

At 10 a.m., the Weather Service reported that the high in San Francisco was already 85 degrees. The high temperature record in San Francisco for this date is 93 degrees, set in 2010.

MORE NEWS: California AG Becerra Warns Of Tacked-On COVID Fees Consumer May Not Have To Pay

Forecasters said temperatures should begin to cool along the coast and bayside starting Tuesday, but inland areas will remain hot through much of the week.