SAN FRANCISCO (KRON) — A Red Flag Warning has been issued for parts of the Bay Area this weekend; the National Weather Service announced on Friday. Critical fire weather conditions are possible from 5 a.m. on Saturday through 5 p.m. Sunday, the NWS said.

Saturday night through early Sunday morning will be the most critical time period, according to the weather service.

Graphic: Kyla Grogan

North-northeast winds are expected to develop early Saturday morning across the ridges of the North Bay, East Bay and Santa Cruz Mountains. Dry offshore winds are expected to peak late Saturday into Sunday morning, the NWS said.

These conditions will result in elevated fire weather concerns. Offshore winds during overnight hours could mix down into interior valleys in parts of the North Bay and East Bay, the NWS said.

Graphic: Kyla Grogan

Wind gusts of 30 to 40 mph are possible with higher gusts up to 50 to 60 mph possible across ridgetops and higher elevations.

Areas affected by the warning include:

  • Marin Coastal Range
  • North Bay Interior Mountains
  • Santa Cruz Mountains
  • Eastern Santa Clara Hills
  • East Bay Hills

The highest ridgetops and peaks could see gusts of up to 60 mph. Minimum relative humidity — as low as 15 to 20 percent — on Saturday and Sunday will combine with windy conditions to elevate fire danger. Conditions of this type can cause fires to grow rapidly in both size and intensity, the NWS advised.

A frost advisory is also in effect for parts of the Bay Area overnight Friday into Saturday.

Graphic: Kyla Grogan

During the Red Flag Warning, the NWS advises against outdoor burning. A Red Flag Warning, the NWS said, means that critical fire weather conditions are occurring now, or will occur soon. Strong winds, low relative humidity and warm temperatures are known factors in extreme fire behavior.