California is under the influence of a cold air mass that could bring the first widespread frost of the winter across the Central Valley, as southern areas see more damaging winds.
The National Weather Service said a freeze watch will be in effect Friday night through Saturday morning in the central and southern San Joaquin Valley because temperatures are forecast to range between 28 degrees and 32 degrees for four to six hours.
A frost advisory will be in effect for the Sacramento and northern San Joaquin valleys, the Sacramento-San Joaquin River Delta and the Mendocino coast.
A hard freeze warning also is in effect for interior San Luis Obispo County valleys.
"We're getting a pretty cold air mass that's dropping down out of Canada,'' said Eric Kurth, a meteorologist with the National Weather Service in Sacramento. "It's going to be the coldest weather we've seen, really, pretty much this year.''
The state capital dipped to 35 degrees in January and February, but the latest forecast predicts temperatures will fall to 32 degrees.
Meanwhile, high pressure in the Great Basin will produce gusty north and northeast winds in Southern California, where days of strong gusts have toppled trees and triggered power outages.
Kurth said it's a good time for residents to cover their plants or move them indoors.
The cold snap comes as most farmers have completed their harvest and early enough that almond and walnut blossoms are not yet out.
Temperatures in the mandarin groves of the Sierra foothills are expected to stay above the level farmers consider a hard freeze, said Rich Colwell, who grows mandarins and Meyer lemons on 3 acres in Penryn, about 30 miles northeast of the state capital.
He said temperatures have to drop into the mid-20s and stay there for four to six hours before citrus farmers become concerned.
"Above that, you're probably OK,'' Colwell said. "I'm not worried now.''
Besides that, recent rains already cut short the mandarin crop by two weeks, said Jim Struble, a third-generation farmer who grows mandarins and clementines on a 3-acre ranch in Loomis, 25 miles northeast of Sacramento.
Saturday morning should be the coldest period of the week, but another cold snap is expected to move in later next week.