Science & Technology

What to expect from the 2021 fire season in the West

After a horrific 2020 fire season, the 2021 season is heating up. Ominous signs popped up early this year: a worsening drought and early heatwaves. The Verge spoke with fire, weather, and climate experts to break down what to expect throughout the year.

The stage is already set for a pretty bad fire season. Up to 9.5 million acres could burn this year, according to a fire season forecast from AccuWeather. That’s 140 percent of the 10-year average. It’s not as much as last year, when more than 10 million acres were scorched. That was the second worst year for fires in the US, in terms of acres burned, since 1960.

The potential for “significant fire activity” is “above normal” for pretty much all of the West at some point this year, according to the latest outlook from the National Interagency Fire Center. A “significant fire” is one that grows so large that locals usually need to call in help from outside the region, according to Nick Nauslar, a fire meteorologist at the Bureau of Land Management. The blaze might span thousands of acres and require hundreds or thousands of personnel to battle it.

But predicting just how bad things will get is still a tough question, so it’s best to break it down into two parts that could influence how this fire season unfolds: known risk factors and wildcards.

A major risk factor is drought. The Western US is in the middle of the most widespread and intense drought in decades. More than 83 percent of the West is in a drought; about half is experiencing “extreme” or “exceptional drought.” In fact, the water level at the Hoover Dam reservoir, the largest in the US, hit a historic low last week.

“This is currently the most exceptional drought that we’ve ever shown on the map in the Western US,” says Brian Fuchs, a climatologist at the University of Nebraska-Lincoln who creates maps for the US Drought Monitor. “When we see droughts like this, it really amplifies the fire season.”

Plants are parched, making them excellent fuel for wildfires. Spring was so hot and dry in California that San Jose State University researchers were shocked in April to find no new growth of the Chamise plant, which they track to monitor moisture content in vegetation. Now, the plants are drying out faster than they normally do, with their moisture content just shy of reaching a record low.

The lower the moisture content, the easier it is for vegetation to catch fire. In that situation, “If somebody drops a match or cigarette, you know, we’re hosed,” says Craig Clements, a professor and director of the Fire Weather Research Laboratory at San Jose State University. Moisture content is closely tied to a fire’s spread rate, or how fast the blaze moves forward. So when that fuel is critically dry, Clements says, fires can get much bigger.

The biggest wildcard is the weather. As of June 1st, there had been fewer acres burned this year than the 10-year average. That’s mostly because there hadn’t been “critical fire weather patterns,” which can be different combinations of high temperatures, strong winds, aridity, and lightning. In 2020, California got an unusual combination of lots of lightning with little rain. That sparked some of the state’s worst blazes, which were fanned by strong gales. California wound up doubling its record for acres burned that year.

“If we transported us back to early to mid-June 2020, we probably have more potential this year than we did last year,” says Nauslar. “The potential is there, but now it’s a matter of if the weather will line up to realize that potential or not.”

Another unknown is people’s behaviors. Do they take extra precautions? Or might they plan an elaborate baby gender reveal that sparks a blaze? “As a resident in a high fire hazard area myself, and as someone who understands how quickly these fires can grow and put people in harm’s way, I definitely look at this upcoming season and say, ‘Okay, we’ve got to be vigilant,” says Crystal Kolden, a former firefighter who is now an assistant professor of fire science at the School of Engineering at the University of California, Merced. “We just have to keep reminding people that if there aren’t any human ignitions, then we don’t have any really big fires.”

A scorching heatwave and high winds this week have fed what’s become the sixth-largest fire in Arizona’s history. Officials listed the cause of the Telegraph Fire burning outside of Phoenix as “human,” but the cause is still under investigation.

Most Western states have already had at least one significant fire this year, according to AccuWeather chief meteorologist Jonathan Porter. “So the season has run ahead of usual, if you will, in that regard,” he says.

Bad weather is starting to make things worse. Hundreds of temperature records fell this week during a sweltering spring heatwave. Salt Lake City, Utah, reached a record 107 degrees Fahrenheit on June 15th. The temperature in Billings, Montana, climbed up to 108 degrees Fahrenheit that day, tying its record. And Texas residents face power shortages as they sweat out the heatwave, just months after deadly blackouts during a freak cold snap earlier this year.

Unlike the Atlantic hurricane season, the fire season in the Western US doesn’t start and end on the same day every year. Unofficially, it’s been thought of as beginning in late spring and lasting through early fall, roughly May to November.

The season hits its peak at different times in different regions. The Southwest typically sees peak fire potential earlier in the season, and then areas further north and west follow. Part of that has to do with what type of vegetation, or fuel, is in each region. Grass tends to dry out faster and then burn earlier. California’s shrubby chaparral takes a little longer to dry out and forests even longer.

Fire season is growing longer, research shows, thanks to changing rainfall and snowmelt patterns. Fire season has lengthened by 75 agonizing days across the Sierras, according to the California Department of Forestry and Fire Protection.

“[Fire season] used to kind of have a better definition,” Nauslar says. “But now I think we’ve been more talking about ‘fire year.’”

The “season” is expected to keep growing longer and more intense as the planet heats up. That’s because climate change is exacerbating many of the risk factors that drive wildfires. Heatwaves are getting more frequent and intense. Typical droughts are becoming megadroughts. Lightning strikes could even become more common. By 2060, the amount of land lit up by lightning-ignited fires could be 130 percent of what it was in 2011.

“Part of me looks at the upcoming season and says, you know, climate change is going to throw some really nasty curveballs at us, every single year,” Kolden says.

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