Traffic
Sonoma County, CA Fog Alert: Visibility Drops to ¼ Mile on US-101
Santa Rosa, CA – Drivers traveling along Highway 101 through Sonoma County and the North Bay face potentially hazardous conditions Monday morning, November 9, as dense fog reduces visibility to a quar
By Mara Ellison · 2026-11-09T09:45:55.919Z
Santa Rosa, CA – Drivers traveling along Highway 101 through Sonoma County and the North Bay face potentially hazardous conditions Monday morning, November 9, as dense fog reduces visibility to a quarter mile or less in some locations, prompting an official weather advisory.
According to the National Weather Service NWS San Francisco Bay Area office, a Dense Fog Advisory is in effect through 9 a.m. Monday for the Sonoma County valleys, particularly along the Highway 101 corridor between Healdsburg and Novato.
Forecasters describe the fog as exceptionally thick, creating dangerous visibility conditions during the morning commute.
Highway 101 Drivers Face Reduced Visibility The advisory includes portions of the North Bay where fog may develop across valleys and major transportation corridors.
Communities near Healdsburg, Windsor, Santa Rosa, Rohnert Park, Petaluma and Novato could experience reduced visibility along affected routes.
The NWS warns that visibility may drop to one quarter mile or less, making it difficult for drivers to see vehicles, intersections and changing road conditions ahead.
These conditions can become especially hazardous when motorists encounter thick fog unexpectedly.
NWS Urges Drivers to Slow Down Motorists traveling through the advisory area are encouraged to reduce speeds and increase following distances.
The NWS recommends using low beam headlights rather than high beams, which can reflect off fog droplets and further reduce visibility.
Drivers should also allow additional travel time and remain alert for sudden changes in visibility.
Commuters traveling between Sonoma County communities and the greater San Francisco Bay Area may encounter delays if fog significantly slows traffic.
When Will Conditions Improve? The Dense Fog Advisory is scheduled to remain in effect until 9 a.m. Monday.
Visibility should generally improve as morning fog dissipates, although conditions may vary across valleys and lower lying areas.
Residents should check current road conditions before leaving and monitor updated NWS information for any changes to the advisory.