The urgent message to avoid traveling during the storm was displayed on signs on highways and freeways across the state on Wednesday.
It's because heavy rains and winds are expected to topple over trees and flood roads. The possible hazards are endless.
"If you can, if at all possible, just postpone that trip, delay it," said California Highway Patrol spokesperson Mike Salas. "Once that car gets into that water, you just never know what is going to happen. A lot of times, we have a mechanical breakdown."
Just this past weekend, Fresno County sheriff's deputies had to rescue a man from rushing waters.
When traveling in higher elevations, even four-wheel drive may not be enough to prevent you from getting stranded in the snow.
That's why you always need to carry chains.
"Every vehicle, regardless of 4-wheel drive, all wheel drive, you have to snow chains in that vehicle at all times and we are going to have personnel up there making sure," Salas explained.
Gas station owners say heavy rains usually result in fewer people at the pumps.
"It's going to be slow, even the last week with the heavy rains, it was slow. Tomorrow, I think it's almost going to be dead," said Nick Augla, co-partner of Fast 'N Esy.
On Wednesday, people did stop by for last-minute items to prepare for the storm.
"Yeah, windshield wipers and propane tanks, they want to keep those things and extra food," said Augla.
Because of the magnitude of this storm, Caltrans has 400 crew members working 12-hour shifts as they continue to monitor rising water levels.