What Is an Urban Firestorm?

Wildfires crossing into urban settings can take homeowners by surprise. Here's how to know if you're at risk, and how to protect your home and family.

Usually when we think of wildfires burning down houses, we think of cabins in the woods. But suburbs and urban areas are increasingly at risk. The December 2021 Marshall Fire in Colorado burned more than 1,000 houses, apartments and businesses, sweeping across big-box store parking lots and a six-lane highway.

The Marshall Fire sparked nationwide headlines about “urban firestorms.” That term may not be scientifically accurate, but it describes the feeling on the ground that day when tens of thousands of people had only minutes to evacuate from thick smoke and fast-spreading flames.

Though not the the first time flames swept through suburbia, the disaster was a wake-up call to many in typical tract-home neighborhoods who didn’t think they were at risk.

“It was the most destructive fire in Colorado history, so that’s new,” says Jim Webster, Wildfire Partners Program Coordinator in Boulder County. “It was also new for us in Boulder County in how far east it was of the mountains.

“We haven’t had catastrophic fires in these communities before. They weren’t in normal high-risk models. They hadn’t experienced fire before, and so they weren’t prepared.”

Why Did the Marshall Fire Burn Neighborhoods?

A wet spring fueled above-average vegetation growth on the grasslands to the West. Then an unseasonably warm and dry summer and fall created tinderbox conditions. An unusual, but not unheard of, windstorm drove the fire into the towns on such a scale it was nearly impossible for firefighters to respond.

Although that sounds like a rare confluence of conditions, it’s happened before, most notably in California — the 2003 Cedar Fire in San Diego, and the 2018 Camp Fire that ravaged the town of Paradise. Science is telling us such catastrophes will be more and more common.

“We utilize proactive methods on our forests to prevent catastrophic fire, like prescribed burning and mechanical thinning,” says Jonathan Groveman, the strategic communications lead for the Forest Service Pacific Southwest Region. “But fires are getting bigger and stronger due to climate change, extreme drought and dryness.”

Even if your home historically hadn’t been been at risk, it may be time to reevaluate the situation.

How Do I Know if My House Is At Risk?

A lot of it has to do with your proximity to flammable forests and grasslands, and if prevailing winds come from those directions. But just because you can’t see vegetation from your window doesn’t mean it isn’t close enough to pose a danger.

“On very windy days, embers can travel more than a mile from the flaming front and ignite homes,” says Webster.

To assess your risk, Webster recommends reaching out to your local governments, which often have maps of wildfire risk areas. They’re sometimes online, or you can talk to your local fire district.

“Wildfire risk maps are only one educational tool,” says Webster. “They include rankings from low to moderate to extreme.

“The messaging from the maps can create a false sense of security. Just because you’re in a low- or moderate-risk area doesn’t mean there’s nothing you have to do, it just means you’re not the most vulnerable.”

What Can I Do if My House Is At Risk?

Once a wildfire jumps into an urban conflagration, prevalent fuel sources switch from natural combustibles to your neighbors’ homes. Because a fire can spread rapidly in those conditions, planning for the worst-case scenario involves:

Home hardening and creating defensible space

Many of the same principles that apply to rural homes also apply in the suburbs. Home hardening includes screening vents so embers are less likely to enter, and cleaning out leaves and other flammable debris from gutters.

Next, create a defensible space. Keep all vegetation at least five feet from your home. Don’t store flammable materials like boxes or gasoline cans next to buildings where embers can ignite them. Expand your efforts, thinning and trimming trees and bushes within 100 feet.

If you need advice, your local fire department or fire prevention bureau may be willing to send someone to walk around your property.

“Your action plan will look a little differently depending on the home itself and the size of the lot,” says Webster. “Creating 100 feet of defensible space is recommended, so individuals with smaller lots will need to work with their neighbors and look at other options for reducing risk.”

Major remodels can also help your home survive a fire. Think about installing a class A roof, fire-resistant siding and tempered double-pane windows.

Enhancing community preparedness

While individual efforts help, a collective effort makes the biggest difference. Webster encourages homeowners to get involved with their homeowner’s association, if they have one. “Sometimes the initiative comes from an individual who says, hey, our community is at risk, and we need to take action to develop a plan to reduce risks,” he says.

Community programs, such as Firewise, are a good resource to help communities better understand and act toward wildfire safety.

“This is new to some people, but will be based on the same basic information, principles and programs we’ve been doing for many years,” says Webster. “It’s now expanding our geographic scope, and fine-tuning specific measures to adapt to the suburban environment.”

Be prepared to evacuate

“It’s not just about saving homes, but saving people,” says Webster. He recommends preparing for the worst. Assemble evacuation go-bags. Have a communication plan within your family and community. Know how to disseminate evacuation notices, what routes to take and what to do after you’ve evacuated.

It’s also good to have a network of neighbors to call with a pet evacuation plan, in case some people are at work when a fire breaks out and can’t make it back to get their pets. The loss of two people and countless pets in the Marshall Fire continues to be a major heartbreak for the community.

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Karuna Eberl
Karuna writes about wildlife, nature, history and travel for magazines, newspapers and websites including National Geographic, National Parks, Discovery Channel, Atlas Obscura and the High Country News. She's also produced a number of independent films and directed the documentary The Guerrero Project, about the search for a sunken slave ship. She and her husband, Steve, wrote an award-winning guidebook to the Florida Keys and are currently completely renovating an abandoned house in a ghost town. She holds a B.A. in journalism and geology from the University of Montana. Member of OWAA, SATW.