Dense fog returns to Fresno and Central Valley. When will it be safer to drive?
Dense fog could make driving dangerous in Fresno, Merced and other Central Valley cities, according to the National Weather Service.
The agency issued a dense fog advisory on Thursday, Feb. 26, warning of thick fog and low visibility starting overnight.
The dense fog advisory goes into effect at 2 a.m. Friday, Friday, Feb. 27, and impacts communities including Fresno, Merced, Bakersfield, Clovis, Hanford, Madera, Porterville Reedley and Visalia.
Here’s what to know:
How long will fog last in Fresno?
The dense fog advisory will remain in effect through 10 a.m. Friday, the weather service said.
“Visibility one quarter mile or less” is possible on local roads, making “driving conditions hazardous,” the weather service said in its advisory.
“Significant travel delays” are expected Friday and Saturday, the weather service said in a Tuesday, Feb. 24, post on X.
The fog comes from high pressure building over central California, the weather service said in an X post on Wednesday, Feb. 25.
Why is it so foggy in 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 26, 2026 at 4:37 PM with the headline "Dense fog returns to Fresno and Central Valley. When will it be safer to drive?."
