Riverside County, already facing a growing wildfire, was placed under multiple extreme weather advisories on Friday as a tropical storm threatened to bring high winds, lightning, flooding and mudslides to the area in Southern California.
By Thursday evening, the Fairview fire had burned more than 27,000 acres of Riverside County, killing two people. Only 5 percent of the blaze has been contained. The state firefighting agency, Cal Fire, had deployed 2,153 firefighters, and more than 18,500 people had been ordered to evacuate.
Emergency officials were also on alert for a looming storm. The National Weather Service placed the county under an excessive heat warning, a flood watch and a high wind warning as Tropical Storm Kay, previously categorized as a hurricane, approached the coast of Baja California in Mexico early Friday.
The overlapping advisories might set off a chain reaction that makes the response to each event more difficult, according to local officials. While they expected the rain to suppress some fires, they were prepared for the storm to bring lightning, which could start new blazes. Strong winds — up to 75 miles an hour in the mountains and desert — could speed the fire’s spread, too.
Firefighters also braced for flash floods and mudslides. The National Weather Service forecast up to seven inches of rain in areas of Riverside County. The blaze, emergency officials said, has made the earth more susceptible to erosion from rain.
Hundreds of officers in the Riverside County Sheriff’s Department were going door to door on Thursday night to enforce the evacuation order, which covered about 18,500 residents around Hemet, a city of 85,000. About 10 percent of the people they had reached complied with the order, the department said.
“We could go from a fire suppression event into significant rain, water rescues, mudslides, debris,” Deputy Chief Jeff Veik of Cal Fire’s Riverside unit said in a news conference on Thursday. “We have challenging days ahead.”
The combination of wildfires and flooding has happened before in California. In 2018, at least 21 people were killed by the sudden flooding and mudslides that followed the Thomas Fire in Santa Barbara County. In 2019, waves of heavy rain in Marin County triggered mudslides in communities that had been scorched by wildfires the previous year, uprooting trees, washing out roads and sending homes sliding down hills.
“The fire makes the soil hydrophobic. It doesn’t absorb water like it usually does,” Shane Reichardt, a spokesman for Riverside County’s Emergency Management Department, said in a phone interview. “There’s also no vegetation to hold the soil in place. So it increases the possibility of mud debris flow.”
“We really just want people to follow the instructions of the public safety officials,” Mr. Reichardt added, “and if they’re under an evacuation order it’s just critically important that they take that order very seriously.”
Gov. Gavin Newsom on Thursday proclaimed a state of emergency for Riverside County for the Fairview fire, currently the largest in California. The declaration also included El Dorado and Placer Counties for the Mosquito fire, the second largest.