US-101, California – Patchy fog has developed across traditional valley locations early Saturday morning, creating hazardous travel conditions for drivers across parts of the San Francisco Bay Area and Central Coast.
According to the U.S. National Weather Service San Francisco Bay Area/Monterey, fog formed overnight and is impacting visibility in localized areas as of 3:30 a.m. Saturday. Drivers may encounter sudden reductions in visibility, especially when traveling through valleys, low-lying areas, and near waterways.
The fog is expected to be patchy rather than widespread, which increases risk because conditions can change rapidly from clear to near-zero visibility within short distances. Morning commuters traveling along major corridors such as U.S. Highway 101, Interstate 80, Interstate 580, California Highway 99, and state routes connecting valley communities may be most affected.
Officials urge motorists to slow down, increase following distance, and use low-beam headlights when encountering fog. High-beam headlights can reflect off fog droplets and further reduce visibility. Extra caution is advised on bridges, overpasses, and shaded valley roadways where fog can linger longer.
The National Weather Service emphasized that fog-related crashes often occur during early morning hours when drivers are unprepared for sudden visibility changes. Allowing extra travel time and remaining alert to changing conditions can reduce risk.
Conditions are expected to improve later this morning as temperatures rise and fog dissipates. Until then, drivers should remain cautious, especially those commuting before sunrise.
For early-morning workers, delivery drivers, and travelers heading toward airports or coastal routes, the fog may briefly slow travel but is not expected to cause long-duration disruptions.
Residents are encouraged to monitor local conditions and additional updates from the National Weather Service as fog coverage evolves through the morning hours.
