The Western United States is likely to see a delayed start to the summer wildfire season after months of rain, snow and cold weather. But the wet winter, which has dramatically eased drought conditions, doesn’t guarantee a low-risk fire year. Destructive fires could still spark in the late summer and autumn, fueled by all the grasses that bloomed because of the downpours and will be ready to burn later in the season.
The latest wildfire outlooks, released this week from the National Interagency Fire Center, show the West with low to normal wildfire risk for at least the first part of the summer. Near-record to record snowpack in several Western states will keep high elevation forests moist for much of the summer, making them less prone to bigger fires.
These maps are a welcome departure from those of recent years, which signaled widespread summer wildfires and competition for firefighting resources. Still, starting in July, parts of the Pacific Northwest could see higher wildfire potential, in part because of lingering severe to extreme drought.
“It will take a long while before the upper elevations across many Western areas are open for large fire business,” said Brent Wachter, a fire meteorologist with the Northern California Geographic Area Coordination Center in Redding, in an email.
Wachter said that May and June are expected to be cooler in California, with intermittent cutoff low-pressure systems, like the weak storm bringing rain and snow to the state this week. However, some models signal that the weather could turn unusually hot later in the summer, possibly due to influences from the rapidly developing El Niño, but that is uncertain this far out.
Summer heat can change the wildfire picture quickly and set up a dangerous autumn in California, when strong, dry winds arrive. Despite a wet winter, three of the most destructive wind-driven fires in state history occurred in 2017 after a hot, dry summer and fall. In 2019 — another wet, snowy year — a slow summer fire season gave way to an active and disruptive autumn because of near-historic windstorms that October.
“My suspicion is that the significant part to the fire season will be delayed in many areas of the West but could finish up fast and furious across the low and mid elevations,” Wachter said. “How furious remains to be seen, and [it’s] too far out for any sort of confidence.”
Lush growth could fuel fires
The perpetual wet weather in 2023 brought a much more robust and lush grass crop than previous years across all of central and southern California, according to Tom Rolinski, a fire scientist with the utility Southern California Edison.
“That’s something that we’re obviously very concerned about,” he said. “That is going to be a big player as we get into later in the summer and of course in the fall because we’re going to have all that extra fuel available to burn.”
The grasses, which seem to be everywhere, could translate into more fires near populated areas this year because they usually result in more ignitions, especially roadside ignitions.
Regardless of what happens with summer temperatures, El Niño and other factors, Southern California will be ready to burn by autumn, if not sooner.
“All of the vegetation you see right now is going be cured out by the fall, for sure, because that’s true every year,” he said.
The big unknowns are how windy autumn will be and when winter rains will arrive to end the fire season. Strong El Niño events can bring a late onset of winter rain while favoring fewer Santa Ana wind days in Southern California, Rolinski said, but it’s still too early to gauge the strength of the developing El Niño.
Legacy of drought remains
Drought may have largely disappeared from official maps, but the legacy of recent severe droughts could also fuel fires this year and for many years to come. There is a massive amount of dead material, not only in Sierra forests but also in Southern California’s native chaparral shrub lands.
Chaparral is built to survive California’s dry summers but not the extended droughts of the past two decades, which have been intensified by climate change.
“The strongest determinant of high fire years is what the drought has looked like over the previous five years,” said Jon Keeley, a senior scientist with the U.S. Geological Survey’s Western Ecological Research Center.
During windy conditions, dead vegetation can enhance fire spread because embers carried beyond the fire front ignite those fuels more easily, he said.
In the area of the destructive, wind-driven 2017 Thomas and 2018 Woolsey fires in Southern California, Keeley and his colleagues found a “huge amount of dieback” that probably helped those fires grow larger.
“I think drought is probably the most underappreciated factor in terms of driving big fire events,” he said.