Critical Fire Weather Conditions Prompt Red Flag Warning for North Bay Hills This Weekend

The threat of high winds and low humidity prompted the National Weather Service on Friday to issue a red flag warning for the North Bay this weekend.

The warning, which means critical fire weather conditions exist or will shortly, goes into effect at 8 p.m. Saturday night and runs through 10 a.m. on Sunday. It covers the hills above 1,000 feet in Napa, Sonoma and Marin counties — with the highest fire danger across the Napa hills and northeastern Sonoma, according to the official alert.

"It's the wind and the relative humidity that makes it more active," said Cal Fire Capt. Jeff Hoag, with the Sonoma-Napa division. "Wind-driven fires are often our most dangerous and destructive."

Two weeks ago, a red flag warning was issued for much of Northern California, which prompted power shutoffs for approximately 48,200 PG&E customers in Napa, Nevada, Placer, Plumas, Sonoma, Butte and Yuba counties. For most of those customers, power was off from early on Wednesday, Sept. 25, until Thursday morning.

PG&E has not yet said if it will initiate any preemptive power shutoffs this weekend.

Whether you're a PG&E account holder or not, you can sign up for phone or text alerts to know when the utility does call for a public safety power shutoff.

The power shutoff program was launched earlier this year in an effort to cut down on potential fire risks during high fire danger periods. You can check PG&E's website and sign up to be notified if the power will be turned off in your area.

A red flag warning is an alert officially issued by the National Weather Service, which then prompts local governments, fire departments and public agencies to take preventive measures.

In addition to the steps PG&E takes, this means many national and state parks will cancel events and close their doors to the public — partially to prevent the possibility of sparking a fire, but also to avoid the risk of having to evacuate hikers or campers if a fire does start.

Fire departments and county agencies also use the warning as a chance to prepare. Hoag said the Sonoma-Napa unit has already added equipment like bulldozers, and has moved hand crews and fire engines to places where fires are more likely.

"We are bolstering our staffing within the unit, additional chief officers, additional firefighters, to respond if they need to," he said.

What Should You Do During a Red Flag Warning?

You should use extra caution when there's a high risk of wildfire.

"No burning, no type of mowing in dry grass in these types of windy conditions," said Hoag. "It goes back to the whole, 'Just one spark can cause a fire.' "

Because a red flag warning indicates a higher fire danger, officials recommend you take the steps you normally would to prepare for a potential wildfire:

• Have an evacuation plan.
• Prepare an emergency bag.
• Be sure pets and family members are ready.
• Avoid using outdoor fire pits or barbecues.
• Avoid parking on dry grass that could spark a flame.
• Follow any instructions or signage indicating closed open space areas.

Hoag said it's the particularly dry inland winds that will make fire conditions so dangerous this weekend, as opposed to moist winds bringing air from offshore.

On Saturday and Sunday, winds are expected to be around 10-20 mph in the North Bay and up to 25-35 mph in the Sacramento Valley, with gusts hitting as high as 45 mph at higher elevations across Napa, Sonoma and Lake counties, said Hoag.

Humidity dipped to just 18-28% overnight, according to the National Weather Service.

Holly McDede contributed to this report.