Dense fog curbs visibility in Sacramento, Central Valley. When will it lift?

Sacramento and other Central Valley communities faced potentially hazardous driving conditions Monday due to a dense fog advisory.

The National Weather Service issued the advisory at 12:59 p.m. Sunday.

It warns of dense fog Monday morning in Sacramento, Modesto and Stockton.

Visibility is expected to be down to 800 feet in places.

The dense fog advisory also affects communities including Fresno, Merced, Kerman, Los Banos, Sanger, Selma, Tulare and Visalia with visibility down to 200 feet.

How long will fog last in Sacramento? Modesto?

The Sacramento area was expected to see fog through noon Monday.

Patchy fog was forecast Monday night, with more dense morning fog and partly cloudy conditions Tuesday.

What about Fresno? Merced?

In the Fresno area, the dense fog advisory also was set to expire at noon Monday.

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.

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 Sacramento’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 2, 2026 at 7:43 AM with the headline "Dense fog curbs visibility in Sacramento, Central Valley. When will it lift?."