Why rains may not prevent dangerous fire season
It's something of a Golden State paradox: Dry winters can pave the way for dangerous fire seasons fueled by dead vegetation, but wet winters — like the one the state has seen so far — can also spell danger by spurring heaps of new growth that can later act as fuel for flames.
Experts say it's too soon to know with certainty what the upcoming fire season has in store. The atmospheric rivers that pounded California in January have left the state snow-capped and wet, which could be a fire deterrent if soils stay damp.
But if no more rains arrive — or if other, less predictable factors such as lightning storms and heat waves develop later in the year — all that progress could go out the window.
“The dice are loaded for a weak fire season, but there are multiple things that could cause it go the other way,” said Park Williams, a bioclimatologist at UCLA.
There's no question the recent rains offered some relief. The storms moved most of California out of the extreme drought categories in which it has been mired for more than three years, and portions of the Sierra Nevada are still buried under multiple feet of snow.
But lower-elevation areas could be at risk, Williams said. That includes the hills around Los Angeles and the foothills of the Sierra Nevada and northern coastal ranges, which are bursting with new grasses that can easily dry out.
“This year, we've loaded up the ground with a whole bunch of new vegetation, and so in summertime — as long as the summer is hot and dry — the probability of grass fires is probably higher this year than normal,” he said.
Capt. Robert Foxworthy, a spokesman for the California Department of Forestry and Fire Protection, said he was so far “optimistic” about the season in higher-elevation areas, where the month ended wetter than in recent years. In 2021, dry conditions paved the way for the Dixie and Caldor fires to become the first to ever burn from one side of the Sierra to the other.
“Obviously, the more moisture we get, the better we're going to be,” Foxworthy said. “The more snowpack we have, the better chance we have of it being a quieter fire season overall.”
But much depends on whether the rest of the wet season brings more rain, he said. Seasonal forecasts are currently inconclusive, pointing to equal chances of dryness or wetness in much of California through April.
If no more rain falls, and if temperatures rise and strong winds arrive, “then I think we'll be in a completely different place come summertime,” he said.
What's more, moisture is only one ingredient in how fire season develops. Many blazes are triggered by heat, lightning, winds and other factors that are harder to predict in advance.
“I can't tell you how many people are going to drive down the road dragging a chain behind their vehicle that may start a couple of fires. I can't tell you if we're going to get a big lightning outbreak … that's going to drop 15,000 lightning strikes in two days, starting a bunch of fires,” Foxworthy said.
There are other factors as well. Many of California's largest fires in recent years have started during intense heat waves, which are becoming hotter, longer and more frequent due to global warming, increasing their likelihood of contributing to conflagrations, said Williams.
Climate change is also contributing to worsening aridification and evapotranspiration, or the processes by which the state's atmosphere is becoming thirstier and sapping more moisture from plants and soil.
“The atmosphere is going to be faster to take the water back, because the air is warmer and more arid,” Williams said. “And so this spring, evaporation rates will be higher than they would have been given the same winter storms in a cooler world.”
Also in the mix is the anticipated arrival of El Niño later this year, said Paul Pastelok, senior meteorologist and lead long-range forecaster at Accuweather. El Niño — a warming of sea-surface temperatures in the tropical Pacific — is often associated with wet conditions in the state, especially in Southern California.
Pastelok said an El Niño pattern could pull more moisture into Southern California in fall and winter, potentially holding back the fire season. But its biggest effect would probably be felt next year as it dampens soils and spurs new growth once again.
The main concern for this year is the timing of the dryness, he said. In fact, the wet start to January could simply push the beginning of fire season later.
“What we notice is at higher elevations, these kind of wet, snowy rushes tend to delay the fire season — it tends to get put off until later-than-normal time periods, probably toward the fall,” Pastelok said. “Whereas the lower elevations, it really doesn't matter much. The soils will dry out quickly, the dry fuels will come on strong as long as there's no interruptions.”
Last year's season also proved how unpredictable fire in the West can be. The state started the year with record dryness, and all signs were pointing to another bad season. Droughtdriven fire seasons in 2020 and 2021 broke records, burning 4.4 million and 2.6 million acres, respectively.
That forecast largely failed to manifest in 2022, with the year delivering one of the weaker seasons in recent memory, 364,000 acres.
That was thanks largely to some well-timed rains that helped dampen burgeoning blazes, as well as a lack of “trigger mechanisms” such as lightning storms and strong wind events, Pastelok said.
Foxworthy, of Cal Fire, said such unpredictability speaks to the challenges of forecasting, especially so early in the year.
“We're optimistic because all the fuels are going to have more moisture in them, but I can't say one way or the other because we don't know what's going to happen from this point until summer,” he said.