Thick tule fog cuts visibility for morning commute in Fresno, Central Valley
Drivers in Fresno and other Central communities faced potentially hazardous driving conditions on Tuesday, Feb. 3, due to thick fog.
The National Weather Service issued a dense fog advisory at 5:46 a.m. Tuesday.
The dense fog advisory affects Fresno, Modesto and Stockton, among other cities.
Visibility was down to a quarter mile or less in places, with “visibility down to zero” in a “worst case scenario,” the weather service said in the alert.
The dense fog advisory also impacts San Joaquin Valley communities including Merced, Los Banos, Hanford, Selma, Tulare, Visalia, Delano, Bakersfield and Taft.
Highways affected by morning fog include Interstate 5, Highway 99, Highway 41 and Highway 180, the weather service said..
How long will fog last in Fresno?
In the Fresno area, the dense fog advisory was set to expire around noon Wednesday. Fresno was expected to be “mostly cloudy” through mid-morning with a high temperature near 65 degrees, according to the National Weather Service’s latest seven-day forecast.
The forecast called for partly cloudy skies overnight and “patchy dense fog” after 10 p.m. The low temperature will drop to around 45 degrees, the weather service said.
Dense fog will blanket the San Joaquin Valley each morning this week with visibility down to zero, according to the National Weather Service’s area forecast discussion.
When will dense fog end in Modesto and Stockton?
Modesto and Stockton were expected to see fog through noon Wednesday.
Why is it so foggy in Northern California and the Central Valley?
These low-lying clouds typically form in the valley during the colder months when winds are light and the soil is moist.
Tule fog becomes especially dense when moist marine air, calm winds and clear skies come together.
“The Central Valley is fertile ground for the formation of tule fog, a persistent radiation fog, in late autumn and winter,” NASA said.
“The perfect recipe for radiation fog ... is for there to be low-level moisture, clear skies and light winds,” said former National Weather Service forecaster Jan Null, a professor of meteorology at San Jose State University.
Null said the area’s early fall weather patterns caused a perfect storm for a particularly heavy fog year.
Driving in foggy conditions
Take extra caution when on the road or avoid driving if possible. If you must drive in foggy conditions, keep the following safety tips in mind, the National Weather Service said:
- Slow down and allow extra time to reach your destination.
- Make your vehicle visible to others both ahead of you and behind you by using your low-beam headlights since this means your taillights will also be on. Use fog lights if you have them.
- Never use your high-beam lights. Using high-beam lights causes glare, making it more difficult for you to see what’s ahead of you on the road.
- Leave plenty of distance between you and the vehicle in front of you to account for sudden stops or changes in the traffic pattern.
- To ensure you are staying in the proper lane, follow the lines on the road with your eyes.
- In extremely dense fog where visibility is near zero, the best course of action is to first turn on your hazard lights, then simply pull into a safe location such as a parking lot of a local business, and stop.
- If there is no parking lot or driveway to pull into, pull your vehicle off to the side of the road as far as possible. Once you come to a stop, turn off all lights except your hazard flashing lights, set the emergency brake, and take your foot off of the brake pedal to be sure the tail lights are not illuminated so that other drivers don’t mistakenly run into you.
This story was originally published February 3, 2026 at 8:28 AM.
