Authorities urged passengers flying out of San Francisco International Airport to check with the airlines on the status of their flights.
"It's been one of those weekends," airport duty manager Shannon Wilson said of the delays caused by the bad weather. "The main issues are the low ceilings, the rain and the reduced visibility."
On Interstate 80 through the Sierra, the main route between Sacramento and Reno, Nev., forecasters issued a winter storm warning, saying that heavy snow and strong winds could create whiteout conditions.
"You should avoid traveling in the mountains today," NWS forecaster George Cline told the Sacramento Bee.
For those making the drive, chains were required on vehicles except four-wheel drives with snow tires from the Placer County community of Gold Run to the Nevada state line.
To the north, chains were also required on stretches of Interstate 5 north of Redding, to just south of the Oregon border.