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 California's heat wave.
Tropical Storm Kay, downgraded from hurricane status, was expected to continue northward off Mexico's Baja California peninsula and then veer west without making landfall in Southern California but still have a strong impact there.
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.
City officials 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.
Windspeeds reached 109 mph (175 kph) on San Diego County's Cuyamaca Peak, the National Weather Service said.
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 Mosquito Fire burned out of control, scorching at least 22 square miles (57 square kilometers) and threatening 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. Fire spokesperson Chris Vestal called the fast-moving blaze an "extreme and critical fire threat."
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The fire's cause remained under investigation. Pacific Gas & Electric notified the state Public Utilities Commission that the U.S. Forest Service placed caution tape around the base of a PG&E transmission pole but no damage could be seen. PG&E 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.
"Based on forecasts, this appears to be a dangerous storm," Bruce Barton, director of the Emergency Management Department, said in a statement.
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.
Operators of California's power grid issued another "Flex Alert" call for voluntary cuts in use of electricity between 4 p.m. and 9 p.m., the hours when demand on the system is at its peak and solar generation is dropping off.
With record demand on power supplies across the West, California snapped its record energy use around 5 p.m. Tuesday with 52,061 megawatts, far above the previous high of 50,270 megawatts set July 24, 2006.
An emergency appeal for conservation that was sent to Californians' cellphones was credited with an immediate drop in demand on the electrical grid Tuesday evening. 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.
Portland General Electric halted power in the Columbia River Gorge and around Mount Hood and a second power company was poised to do the same Friday. More than 40,000 customers were likely lose power in planned shutoffs as winds of up to 60 mph (97 kph) hit some areas.
Authorities urged residents to charge cellphones and be ready to evacuate. Power shut-offs due to extreme fire weather, common in California, are new to the Pacific Northwest.
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Antczak reported from Los Angeles. Associated Press writers Stefanie Dazio and Christopher Weber in Los Angeles and Gillian Flaccus in Portland, Oregon, contributed to this report.

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