Dense fog is creating dangerous travel conditions across California’s San Joaquin Valley, prompting a Dense Fog Advisory that remains in effect through noon Thursday, according to the National Weather Service in Hanford.
The advisory warns of visibility frequently dropping below 200 feet and at times near zero, particularly during overnight and early morning hours. The National Weather Service classifies the event as a Level 5 out of 5 transportation risk, the highest category on its Experimental Fog Severity Index.
Impacted roadways include State Route 99, Interstate 5, State Route 41, State Route 180, State Route 168, State Route 152, and State Route 198, which serve as major commuter and freight corridors through Fresno, Kern, Tulare, Merced, and Kings counties. Officials report that sudden visibility reductions may lead to stopped traffic with little warning.
According to the National Weather Service, dense fog is expected to redevelop each night and morning through the remainder of the week, with only partial clearing possible during afternoon and early evening hours. The fog is most persistent in low-lying areas and near agricultural zones where moisture remains trapped near the surface.
Transportation officials urge drivers to slow down, use low-beam headlights, and increase following distance. Motorists who encounter rapidly deteriorating visibility are advised to exit the roadway safely rather than stopping on highway shoulders, where rear-end collisions are more likely.
The fog event may also impact early-morning school travel, agricultural transport schedules, and young workers commuting before sunrise. Commercial drivers operating along CA-99 and I-5 are encouraged to adjust routes or delay departures when possible.
The advisory is based on updated analysis issued at 1:40 p.m. Tuesday, with forecasters noting high confidence in continued fog development through at least Thursday morning.
