Locals reported hail in Culver City, downtown L.A. and Pasadena. The California Highway Patrol reminded motorists to slow down and turn on their headlights.
In the mountain areas, temperatures could drop below 32 degrees Fahrenheit on Wednesday. Antelope Valley is expected to see similar conditions on Saturday. This prompted a cold weather alert from the L.A. Department of Public Health.
The first snow of the season is in the forecast on Wednesday and Thursday for Los Angeles County mountains.
Snow will fall in areas with elevation as low as 5,500 feet, with the eastern San Gabriel Mountains expected to receive up to 6 inches of snow, according to the National Weather Service.
Forecasters issued a winter weather advisory effective 7 a.m. Wednesday to 7 p.m. Thursday for Acton, Mount Wilson, Sandberg, and other L.A. County mountain communities, excluding the Santa Monica Mountains.
Officials urged the public to take precautions in preventing carbon monoxide poisoning by only using approved heaters and installing a carbon monoxide detector. They also reminded pet owners not to leave their animals outside overnight.
In San Bernardino and Riverside counties, mountain areas are under a winter storm warning from 7 a.m. Wednesday to 7 p.m. Thursday. Communities affected include Lake Arrowhead, Big Bear City, Big Bear Lake, Running Springs, Wrightwood and Idyllwild-Pine Cove.
Up to 16 inches of snow could fall on higher peaks, according to forecasters. Transportation officials recommended motorists to check for chain requirements on state routes 330 and 18 in the San Bernardino mountains.
The cooler weather arrives just days after parts of Southern California experienced record heat in the 90s.