Officials warn of extreme holiday driving conditions in California

"Californians looking to traverse the state by car during the holiday week can expect to face a potentially historic dose of wet weather and should exercise extreme caution - and even be ready to alter travel plans, Caltrans officials said. The agency has been preparing for months for a perfect storm like this, when some of the busiest travel days of the year coincide with a weather pattern that portends the state's most prolific rainfall in decades, Caltrans spokesperson Kevin Drabinski told SFGATE via phone Monday."

""It really starts in the fall, where we're meeting and discussing potential areas of concern, where to deploy equipment and services to respond," Drabinski said of the agency's preparation work, noting that a key component in keeping the state's major roadways safe is one drivers often overlook: culverts beneath the roads. "Culverts are the real heroes of the state highway system. A culvert that is clear will diminish the chance of flooding and keep the highway open," he said of these tunnels used to divert water."

""As of Monday afternoon, flood watches remain in effect for 41 million people, encompassing nearly all of California and parts of southern Nevada and northwest Arizona," NBC News reported Monday. "Cities at risk include San Francisco, Los Angeles and San Diego. A potent atmospheric river is fueling the flooding and will continue throughout the week, with the moisture plume beginning to move toward Southern California.""

California faces potentially historic rainfall during the holiday week as a potent atmospheric river increases flood risk across nearly the entire state and neighboring regions. Caltrans has prepared for months to respond during peak travel days and emphasizes culvert maintenance as critical to preventing roadway flooding. Rain, sleet, ice and persistent fog create dynamic hazards that can change rapidly and complicate travel. Flood watches cover tens of millions of people and place major cities at risk. Drivers are urged to use Caltrans QuickMap before and during trips, exercise extreme caution, and be ready to alter travel plans.

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