Forecasters warned that a low pressure trough sinking over San Diego County and parts of neighboring Orange County could keep nightly temperatures below the freezing point in coastal areas, the low deserts and inland valleys, threatening orange, avocado orchards and other sensitive plants. The coldest nights were expected to hit Friday and Saturday.
Farmers were prepared to pull out giant fans to circulate the frosty air and keep it from settling on their citrus trees, said Eric Larson of the San Diego County Farm Bureau. Other growers were placing soft cloth over their strawberries and flowers. The National Weather Service predicted overnight lows in the 20s in the lower deserts and key citrus-growing regions in the Central Valley, and in the 30s along the coast.
"These guys are going to be up all night watching thermometers," Larson said.
Freezing temperatures weren't the only weather challenge in Southern California, a region boasting one of the planet's most temperate climates.
Forecasters say a combination of astronomical high tides, high surf and strong winds will bring minor flooding to low-lying areas of the Southern California coast. The weather service issued coastal flood advisories for all counties from San Luis Obispo south to San Diego through Saturday morning.
They also warned motorists to watch out for sand blowing across coastal highways and snow in the mountains down to 2,000 feet. Snow briefly closed the Grapevine section of Interstate 5 north of Los Angeles twice on Thursday. Several accidents and spinouts were reported in the mountain pass as the winter weather bore down on Southern California.
Winds could gust to 60 mph there and up to 45 mph in valleys and coastal areas. Highs will only hit the 50s and 60s and rain showers are expected throughout the region.
Families pushed aside boogie boards and pulled out sleds as snow fell Thursday in the mountains of San Bernardino and Riverside counties. Chains were required on all vehicles.
Farther north in Sonoma County, homeless shelters started handing out extra warm clothes to protect the least fortunate from below-freezing overnight temperatures.
Jennielynn Holmes of Catholic Charities in Santa Rosa told the Santa Rosa Press-Democrat the waiting list to get in her three shelters doubled Wednesday morning. John Records, who runs the Mary Isaak Center in Petaluma, said he planned to put out extra sleeping mats and make more space for people.
"It's terrible to be on the street in weather like this," Records said. "People anticipate it and they find a safe place to be."
Workers at SeaWorld in San Diego planned to crank up the heat for their macaws, toucans and parrots. San Diego zookeepers were also heating rooms for chimpanzees, apes and other tropical animals.
"They'll probably be huddling together and not be in areas where people will be able to see them," said zoo spokeswoman Christina Simmons.
Many local residents planned to do the same.
"We'll have to huddle up, drink coffee, and tell stories," joked J.P. Pierre, owner of Surfy Surfy Surf Shop in the beach town of Leucadia. "But there's a no whining rule around here because I have so many friends from the northeast and Canada. If everyone had a decent jacket it would be no big deal, but everyone is walking around in flip flops."
The so-called king tides will peak Friday morning around 7 feet, depending on location. The conditions may cause some flooding across beaches, parking lots and around estuaries, lagoons and harbors. Parts of Pacific Coast Highway between Sunset Beach and Seal Beach could see standing water.
San Diego's Mission Beach was nearly empty Thursday except for a few snowbirds who scoffed at a cold snap that seemed downright balmy to them. Some shot pictures of the wind-swept waves.
"We're from Chicago, so to us this is like a heat wave," said Rod Erdohaty, 54, walking to the beach in blustering wind.