Traffic
Fresno, CA Fog Alert Nov. 4: Visibility Near Zero on Highway 99
Fresno, CA – Drivers across California's San Joaquin Valley face potentially dangerous travel conditions Wednesday morning, Nov. 4, as dense fog reduces visibility to one quarter mile or less along ma
By Erin Vale · 2026-11-04T11:21:43.396Z
Fresno, CA – Drivers across California's San Joaquin Valley face potentially dangerous travel conditions Wednesday morning, Nov. 4, as dense fog reduces visibility to one quarter mile or less along major highways. Forecasters have identified a Level 4 out of 5 transportation impact risk, raising concerns about significant traffic disruptions.
According to the National Weather Service NWS in Hanford, a Dense Fog Advisory is in effect from midnight until 10 a.m. Wednesday for much of the San Joaquin Valley, with particularly hazardous conditions expected along the Highway 99 corridor.
Level 4 Travel Risk Across the Valley
The NWS experimental Fog Severity Index highlights a high transportation risk, particularly around communities along Highway 99, including Fresno, Madera and Merced.
At Level 4, visibility can deteriorate to approximately 800 feet or less, creating conditions where traffic may slow dramatically or stop unexpectedly.
Other major routes potentially affected include Interstate 5 and California highways 41, 43, 140, 152, 180, 198 and 33.
Morning Commutes Could Face Delays
The most concerning conditions are expected during the early morning hours, when commuters and commercial truck drivers may encounter sudden visibility reductions.
Motorists traveling between Fresno, Bakersfield, Visalia and communities throughout the Central Valley should prepare for changing road conditions.
The NWS recommends reducing speed, increasing following distance and switching headlights from automatic settings to low beams when driving through dense fog.
Drivers should avoid using high beams, which can reflect off fog droplets and further reduce visibility.
When Will Conditions Improve?
The advisory is scheduled to expire at 10 a.m. Wednesday, although fog may persist in isolated areas depending on local conditions.
Travelers should allow additional time for morning trips and monitor traffic advisories before departing.
For updated weather alerts and forecasts, visit weather.gov/hnx.