(CNN) — More extreme weather is in the forecast for California this week as a hurricane spins in the Pacific Ocean off the coast of Mexico.
As Hurricane Kay moves north, it could bring heavy rainfall and the threat of flash flooding. And — far from providing relief from California’s extreme heat — the hurricane’s winds could actually push temperatures higher in some locations.
Kay is forecast to track north, parallel to the Baja California peninsula, through Friday. It’s expected to turn west, away from the coast, right around the U.S.-Mexico border.
Kay is expected to remain at hurricane strength until about 250 miles from San Diego, something only four other storms have done since 1950, according to the National Weather Service.
The last time a hurricane came that close to California was 1997’s Nora. At hurricane strength, Nora made a second landfall in Baja California about 250 miles southeast of San Diego. It entered the United States as a tropical storm at the California-Arizona line, and was downgraded to a depression over Vidal Junction, in San Bernardino County. It brought torrential rain and flooding to Arizona, California and Nevada.
The storm doesn’t need to be hurricane strength “for this to be a major concern for Southern California,” said Brandt Maxwell, a San Diego NWS meteorologist.
Forecasters warn the system could amplify the region’s extreme heat woes, rather than relieve them.
Winds could gust more than 60 miles per hour as the system interacts with the mountainous terrain of Southern California. And those winds will be coming from the east, which means they will have a warming effect on coastal cities. As air travels down mountains, it is compressed and its temperature rises.
It will be similar to the Santa Ana wind phenomenon, which typically occurs in the fall and winter.
“We are not calling it Santa Ana winds, but they will have characteristics of them as they pass through canyons and the sloped terrain,” Maxwell told CNN.
The warm, dry winds from the east will increase the region’s fire risk. Temperatures could reach 100 degrees in the coastal areas of San Diego and Orange counties on Friday.
“This happened in 1984 as Category 1 Hurricane Marie well southwest of San Diego County forced temperatures to reach 100 in San Diego,” Maxwell said.
Overnight lows could remain in the 80s overnight Thursday and into Friday morning, making sleeping uncomfortable, especially for those without air conditioning.
Then, the relentless heat will “end abruptly and unusually” late Friday, the Los Angeles NWS said, as the tropical system’s cloud cover and rainfall move into the region, drastically reducing temperatures but creating new hazards.
Even as the Southwest has been mired in a multi-year megadrought, Kay’s rainfall could pose a significant flood threat.
“Confidence is rapidly increasing for a significant rainfall event across Southern California, Arizona, and eventually central California and Nevada into Saturday,” forecasters at the Weather Prediction Center wrote Wednesday.
East-facing slopes near the Santa Rosa and San Jacinto mountain ranges could see the heaviest rainfall, with as much as 4 inches possible through Friday. The WPC has issued a rare level 3 out of 4 outlook for excessive rainfall across this region for Friday.
Even though rainfall is desperately needed across parched Southern California, this much rain over a short period of time can cause creeks and rivers to rise rapidly.
“It’s never a good thing to get too much rain all at once, a trait all too common among slow-moving tropical storms,” the WPC said. “Thus, the flash flood potential is summarily also rapidly increasing.”
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