Red Flag and Extreme Fire Weather warnings: What they are and why they matter

Bay Area fire officials and weather experts say getting residents to take the alerts seriously is an ongoing challenge — and has never been so important.

A red flag warning of increased fire danger flies at the Oakland Fire station No. 17 on High Street on Aug. 17, 2021.
A Red Flag warns of increased fire danger flies at the Oakland Fire station No. 17 on High Street on Aug. 17, 2021. Credit: Brian Krans

Nicholas Luby has lived on Skyline Boulevard for the last 16 years and is still shocked by how many of his neighbors in the hills don’t know what a “Red Flag Warning” means.

“I have neighbors that have lived up there longer than I have and they’ve said to me, ‘Oh, what does that mean?’” the deputy chief of the Oakland Fire Department said. “It kind of catches me off guard. You’ve lived here for how long and don’t know what a red flag is?”

Ceremoniously, a Red Flag Warning means firehouses fly a red flag below the stars and stripes that reads: “FIRE WEATHER.” But those who issue the warnings wish more people knew of their significance.

The National Weather Service announces Red Flag Warnings when dry, hot, and windy weather creates the potential for severe fire behavior. That typically happens about 20 to 30 times a year in the East Bay hills and other nearby areas where wildlands butt up against residential areas. 


Such was the case during the Oakland firestorm in October 1991 that killed 25 people and destroyed nearly 3,500 homes and apartment units over two days. The combined loss of life, injuries, and economic loss—what would be more than $4.4 billion today—made it one of the worst fires in American history. It wasn’t technically classified as a wildfire because it started and spread in populated areas.

Conditions have only gotten worse in the three decades since then. Fire season in California is now considered a year-round event, and every year more homes are built in areas prone to wildfires. The state is again in the midst of a severe drought and is already experiencing record-breaking wildfires heading into the height of fire season.

Given these conditions, fire officials are experimenting with new ways to impress on residents the danger of wind-powered fires. 

The Berkeley Fire Department is now declaring “Extreme Fire Weather” on the most dangerous Red Flag days, when strong winds and low humidity are forecast, creating “especially risky conditions.” Since 1991, it says, every major fire threatening the East Bay has started under these conditions. During Extreme Fire Weather, Berkeley Fire strongly recommends you leave the hills — even before a fire starts.

Firefighters cannot control a wind-powered fire, Assistant Berkeley Fire Chief Keith May said. “That’s like asking a fire engine to go out and stop a tornado.” 

Not only the hills are at risk

Fire danger notice outside Berkeley Fire Department Station 7  in the Berkeley Hills on August 10.
Fire danger notice outside Berkeley Fire Department Station 7 in the Berkeley Hills on Aug. 10. Credit: Clara Mokri

In the East Bay, there is no longer any reason to think that fires are only a threat in the hills — not when extreme weather and wind conditions in California are reducing our ability to contain them. In 2018, the Camp Fire in Butte County expanded 5,000 acres over the course of one three-hour period — roughly the equivalent of a football field every three seconds — according to Cal Fire.

“The reality is with climate change and the new norm we’re seeing, communities we thought were sheltered from that potential are definitely in the target zone,” Luby said. “What we can’t control is the weather, and the weather is changing.”

The most obvious recent example, Luby said, was the Tubbs Fire in 2017 in the North Bay, where near-hurricane-level winds powered flames over U.S. Highway 101 and “annihilated” the bedroom community of Coffey Park in Santa Rosa. It started as a wildfire, but soon the flames were so intense that they used houses for fuel, casting rich, burning embers far ahead in front of the fire and reducing neighborhoods in its path to nothing but foundations and ash.  

“The vegetation is what got it started, allowed the freight train to get going, allowed the embers to get creative and move a half-mile ahead,” he said. “These fires get so fast and so hot that they move with such velocity and intensity.”

Luby said just last year he was working out of the High Street firehouse and felt hot blasts of wind come down from the hills that could have easily brought embers and flames across Interstate 580 and into the Oakland flatlands. 

“That’s the scary part about wildfire and how the weather is currently changing with climate change,” he said. 

Wildfires in Northern California over the last four years have continued to surpass records for acres burned and destruction caused, and residents and officials continue to wonder when the East Bay hills will again suffer a similar fate.

That’s why fire officials want people to be familiar with and heed Red Flag and Extreme Fire Weather warnings. Red Flag Warnings were issued for different areas of California nearly every day during the month of July, Luby said, something that was “unprecedented five years ago.” 

Heeding Red Flag Warnings

A neighborhood fire hydrant in the Berkeley Hills.
A neighborhood fire hydrant in the Berkeley Hills. Credit: Clara Mokri

David King is a meteorologist with the National Weather Service in Monterey, the office that issues Red Flag Warnings for Alameda, Contra Costa, Sonoma, and Napa counties. He said those designations are not made lightly, considering they signal to fire and other first responders to staff up because weather conditions are primed for the worst possible scenarios. 

“It’s a big decision,” King said. “It’s not a hazard we use flippantly.”

First, the NWS issues a fire weather watch, signifying severe weather could produce fire-spreading weather over the next 12 to 72 hours— a signal to first responders to start preparing for a possible large fire.  

Red Flag Warnings cover the subsequent 24 hours. The NWS issues them for two main reasons, the first being offshore winds, or when winds from drier inland areas like the Central Valley blow west over heavily wooded terrain like that of the East Bay hills. “That dry air is actually drying out these fuels,” King said. 

The second reason is for “elevated convection,” or a dry thunderstorm that can cause lightning. Such was the case in August 2020 when a rare lightning storm ignited 650 wildfires, mostly in Northern California. The Bay Area dodged a similar storm during a Red Flag Warning in July 2021.

But, as King notes, predicting where lightning strikes will occur is nearly impossible. “We just know where the conditions for a fire exist,” he said. 

The Berkeley Fire Department is alone in the East Bay in putting residents on higher alert during the most dangerous Red Flag days.

While Berkeley saw 25 Red Flag days in 2020, just two of them were Extreme Fire Weather days. The Berkeley Fire Department recently took a close look at larger hill or wildfires in the Berkeley-Oakland region dating back to the 1991 Oakland firestorm, and similar to historical research by the Hills Emergency Forum, found that the most severe wildfires in this area all happened during Extreme Fire Weather.

“People don’t realize how fast” fire can travel, Luby said. “You could have five minutes to get out, not five hours.”

How to be prepared

Many Red Flag, and even Extreme Fire Weather, warnings won’t manifest as fires. As a result, when they are given, it may not seem like there’s an immediate threat.

“One of the challenges is getting the community to take the messaging seriously and do what they need to do to make sure they’re prepared for a fast-moving, rapid-expanding wildfire,” Luby said. “That’s why the National Weather Service issues it.”

Luby said there are advantages to living in an urban-wilderness interface like the East Bay hills that is close to nature and has beautiful views, but it’s not without its risks. 

The best way to handle that risk, said Luby, is to not panic but “do everything you can to plan and prevent.” 

As a hills resident, Luby doesn’t leave his kids at home alone during Red Flag days, even if he’s just running to the store. That’s because he’s seen winds increase by 30 miles an hour in just 15 minutes. He recommends people leave their bedroom windows cracked open so they hear the emergency sirens if it’s time to evacuate, and keep phones fully charged with do-not-disturb mode turned off. 

Assistant Berkeley Fire Chief Keith May’s plea to people in hillside fire zones is to seriously consider preemptively relocating during Extreme Fire Weather. Especially, he says, people with mobility problems, large families or anything that could slow an evacuation.

The preemptive relocation guidance is also tied to obstacles posed to firefighters by the Berkeley Hills’ mountain topography, dense vegetation and many narrow, winding roads. “When these roadways are packed with cars and people trying to escape a fire, it will be really difficult for us to get responders up into the hills to fight the fire,” May said.

Officials are searching for language strong enough to communicate how dire their advice is to preemptively relocate during Extreme Fire Weather and Diablo winds. Berkeley Fire has urged residents to “take as much responsibility as you can” and “control your own destiny.”

Relocating on all Red Flag days may make the most sense for you, with fire experts getting louder with this line of advice.  

“Whether people believe in global warming or climate change, these large fires are increasing. People typically only leave after a fire starts,” May said. “We’re trying to cultivate a new mindset.”

Preemptively relocating may mean staying with friends or family somewhere outside of the fire danger zone. Several Berkeley hotels have offered discounts on Red Flag days, targeting people relocating from high-risk fire zones.

Getting alerted

Red Flag Warnings are broadcast out through the AC Alert system to those who have signed up for the service (it’s free) and are also announced through local media.

If a Red Flag Warning is issued for your area, fire officials recommend the following:

  • Keep your phone on, charged, and in your pocket throughout the day. 
  • Park outdoors with your tank full of gas and your trunk packed with your go bag—one for each member of your family—and extra water. (Garage doors that operate on electricity may not open if the power goes out.)
  • Upload important documents (insurance policies, etc.) to the cloud.
  • Avoid activities that could cause a spark. 
  • Be prepared to rapidly evacuate if needed. 

Kate Darby Rauch contributed reporting to this story.