Firefighters and residents in the Foresthill community of Placer County, Calif., watch the as a plume rises from the Mosquito Fire on Thursday, Sept. 8, 2022. (AP Photo/Noah Berger)

SAN DIEGO (AP) — A tropical storm nearing Southern California on Friday brought fierce mountain winds, high humidity, rain and the threat of flooding to a region already dealing with wildfires and an extraordinary heat wave that has stressed the electrical grid.

In a mix of bad and good, firefighters feared powerful winds could expand the massive Fairview Fire 70 miles (113 kilometers) north of San Diego, while forecasters said the change in weather would finally end the state’s heat wave.

Tropical Storm Kay, downgraded from hurricane status, was starting to sputter as it moved northward off Mexico’s Baja California peninsula and was expected to keep losing steam overnight and head farther out to sea without making landfall in Southern California, according to the National Hurricane Center. But it was still having an impact there. The National Weather Service warned of a threat of flash floods for much of Southern California, Arizona and southern Nevada.

The moisture was forecast to then surge farther north into the Central Valley and the Sierra Nevada, where the dangerous Mosquito Fire is burning, bringing both significant cooling and the possibility of thunderstorms during the weekend.

The tropical conditions added a swelter to the heat wave, which offered little overnight relief. The San Diego airport was 89 degrees (31.6 degrees Celsius) with rain at 5 a.m. Friday.

“Living in San Diego, it’s odd to see skies overcast and rain and go outside into a wall of humidity as if it were South Carolina,” said city spokesperson Anthony Santacroce.

Officials from San Diego to Long Beach were posting warning signs in low-lying coastal areas and making sandbags available to the public. Crews were on standby to deal with any flooding, while the forecast of rough seas prompted the cancellation of afternoon and evening ferry services Friday to Catalina Island, off the coast of Los Angeles.

By late morning a steady rain pelted downtown San Diego as Charles Jenkins swept the accumulating puddles away from the tarps of his makeshift home.

“The heat was killer so for now this feels good,” Jenkins said. “I just hope the water doesn’t get too high. But I will rough it. I’ve got pallets I can put underneath to keep out the rain.”

Around 1 p.m. as the rain continued, a Navy contracted, twin-engine plane carrying two civilian pilots slid off the end of a runway after it touched down at Naval Air Station North Island in Coronado and parked in a spit of sand. The plane’s nose was damaged but the pilots were able to depart on their own and were taken to a hospital for observation, Naval Base Coronado spokesperson Kevin Dixon said. The cause of the crash was under investigation and it was unknown if weather was a factor.

To the east in the agricultural region of California’s Imperial Valley near the Mexican border, there was some scattered flooding of roads and fields and power outages, officials said.

Windspeeds reached 109 mph (175 kph) on San Diego County’s Cuyamaca Peak, the National Weather Service said. Several small school districts in the mountainous region called off classes to keep people from having to travel in the blustery weather.

The gusts made driving to work difficult for Rhonda Young, office manager of the Julian Pie Company in Julian, a mountain town 60 miles (100 kilometers) northeast of San Diego that is known for its apple orchards.

“It’s pretty crazy out there,” she said. “There are definitely a lot of trees down.”

The winds added a major concern on the fire lines.

The Fairview Fire covered about 43 square miles (111 square kilometers) of Riverside County and was just 5% contained. Two people died while fleeing on Monday and at least 12 structures have been destroyed. More than 18,000 homes were threatened.

To the north in the Sierra Nevada, the fast-moving Mosquito Fire doubled in size Friday to at least 46 square miles (119 square kilometers) and threatened 3,600 homes in Placer and El Dorado counties, while blanketing the region in smoke.

Flames jumped the American River, burning structures in the mountain hamlet of Volcanoville and moving closer to the towns of Foresthill, home to about 1,500 people, and Georgetown, population 3,000. More than 5,700 people in the area have been evacuated, said Placer County Sheriff’s Office Lt. Josh Barnhart.

David Hance slept on the porch of his mother’s Foresthill mobile home when he woke up to a glowing red sky early Wednesday morning and was ordered to evacuate.

“It was actually fricking terrifying, cause they say, ‘Oh yeah, it’s coming closer,'” he said. “It was like sunset in the middle of the night.”

Hance left behind most of his electronic gear, all his clothing and family photos and fled to Auburn, where he found his mother, Linda Hance, who said the biggest stress is wondering: “Is my house still there?”

The fire’s cause remained under investigation. Pacific Gas & Electric said unspecified “electrical activity” occurred close in time to the report of the fire on Sept. 6.

Positive news was reported from the Radford Fire near the Big Bear Lake resort area in the San Bernardino Mountains east of Los Angeles. Evacuation orders were reduced to warnings as containment grew to 59% with just under 2 square miles (5 square kilometers) burned.

While rain could help quell the fires, the storm raised new risks.

Riverside County officials warned that some areas including wildfire burn scars could get up to 7 inches (17.7 centimeters) of rain, bringing the threat of flash flooding and mud and debris flows.

Southern California Edison advised that it was considering cutting power to some areas due to the weather. Public safety power shutoffs are used to prevent fires from igniting if winds bring down or damage power lines and electrical equipment.

Up the West Coast, Oregon utilities began shutting down power to thousands of customers on Friday as dry easterly winds swept into the region, raising the risk of wildfire danger.