Fuel. Topography. Wind. Temperature. Humidity.

Sometimes they all coalesce in the worst ways possible, creating a blaze so destructive and deadly that entire towns are engulfed without warning. That was the case in California this weekend, when the Camp Fire destroyed the town of Paradise, and another swept through hundreds of homes near Malibu. Statewide, at least 44 people have been killed, with more than 200 people still missing. Some 7,500 homes and buildings have been lost.

But there’s one factor that can’t be qualified, quantified, studied or predicted: an element of firefighting that may one day run out in Eastern Washington.

“We’ve been lucky,” said Spokane Fire Chief Brian Schaeffer. “Very, very, very lucky.”

Similar to California, Washington and the rest of the Pacific Northwest have been dealing with an increasingly extended and costly fire season – spurred by rising temperatures due to climate change. This year was the worst wildfire season on record, with more than 1,700 wildfires reported – most of which started in Eastern Washington.

But unlike California, Washington’s fire season typically ends in October, mostly due to colder temperatures and humidity. And with a population of about 7.5 million that pales in comparison with California’s 40 million, it’s less likely for towns and homes to be in the direct path of wildfires despite the blazes regularly burning several hundreds of thousands of acres in the center of the state.

Still, fire experts agree it’s not a matter of “if” a fire of the magnitude of the Camp Fire could happen in Eastern Washington and Spokane. It’s a matter of “when.”

“That’s the bad news,” said Andy Perleberg, who leads the extension forestry program at Washington State University. “But there’s a couple of things working with us.”

Perleberg said California fires are particularly problematic as compared with Washington’s. First, they feed on an explosive brushland vegetation that is not only exceptionally flammable, but regrows quickly after a fire moves through, setting itself up to burn again in a year’s time. And the state, as a whole, is much hotter and drier than Washington.

Then there are the hills and wind. In Southern California in particular, he said, the Santa Ana winds, which can easily exceed 40 miles per hour, are perfectly suited to carry embers several miles, spreading fire with unmatched speed. And with population growth leading people to build homes farther and farther into forested areas, he said fires don’t need to burn as long or as far before finding a home.

And yet, as the instructor said that as he paced his own property recently in Cashmere, on the eastern side of the Cascades near Wenatchee, he was struck by how easily it could all burn to the ground, given the right circumstance of fuel and wind.

“So why we haven’t had it yet? My guess is it’s just a matter of time,” he said. “And I’m not trying to scare anybody. This is a real scenario.”

Guy Gifford, spokesman for the Washington Department of Natural Resources northeast region, said this year Eastern Washington experienced its highest number of fire starts since at least 2008, with 1,389 blazes – a new high in a five-year trend that’s seen a yearly increase since 2013. Only 140 of them, or 10 percent, were started by lightning, he said. The rest were by humans.

However, he said Spokane County is well-suited to avoid a catastrophe, though he didn’t rule out the possibility.

“Our fuels are pretty dry,” he said. “But topography matters. It’s relatively flat until you get to Mount Spokane.”

Since 1902, one of the state’s most destructive fires in terms of structures lost was 2014’s Carlton Complex Fire, which burned into the towns of Pateros and Brewster in Okanogan County, destroying more than 300 homes. Two people died, though they were not killed by the fire. One man had a heart attack, and another fell off his bulldozer defending family property.

Schaeffer, who has led the Spokane Fire Department since last year, said that particular blaze left an impression on him. As did the Spokane Firestorm of 1991, when 50-mph winds and dry temperatures combined to create walls of flames that burned more than 110 homes and killed two people across the region.

Knowing how unpredictable summer wildfires can be, he said local, state and federal agencies need to be more proactive in prevention, rather than reaction.

“Oftentimes, being lucky encourages bad behavior,” he said. “And from a fire chief standpoint, we’ve been lucky a lot in the state of Washington.”

Perleberg and Schaeffer said one of the best ways to mitigate destructive wildfire spreading is forest management. By thinning a forest, creating gaps and limiting brush that can send a fire vertical, they said firefighters typically have a much easier time putting the blaze to rest before it has a chance to grow.

“From a forestry perspective, reduce the amount of fuels,” Perleberg stressed. “And this isn’t going to cause a desert scape by any means. This is just selecting the right types of vegetation that would occupy your homeland.”

And if a fire were to jump to structures in the city proper, forcing citywide evacuations by the thousands, city officials say an emergency plan is in place, though it depends on the location of the fire.

In the case of the California fires, several residents posted pictures and videos showcasing their harrowing escape from their homes as walls of flames engulfed both sides of a road. In several cases, the residents said they had little or no warning that fire was approaching.

Marlene Feist, city spokeswoman, said a countywide emergency plan is put in place specifically to avoid last-minute evacuations.

“If we had to evacuate the whole city, I guess we’d have to determine where we’re evacuating them to – to the east or west, and implement that plan,” she said. “And then publicize ways out of the community. We all work together, the county, the city, the hospitals, everybody.”

While wildfires are certainly one of the city’s top planned hazards, Feist said Spokane also contends with the possibility of windstorms, ice storms, derailed freight or oil trains over the downtown core, and an Interstate 90 viaduct collapse.

“You basically look at all the things that could happen, prioritize them on the likelihood of those happening, and you plan around that,” she said. “And of course, wildfires.”