A massive chain‑reaction crash involving as many as 150 vehicles shut down both directions of Highway 99 in Central California on Saturday morning, trapping drivers in near‑zero visibility and sending at least 10 people to area hospitals as dense tule fog once again smothered the San Joaquin Valley.
The California Highway Patrol began receiving panicked calls from motorists near Earlimart, California, shortly after 8:15 a.m., reporting multiple collisions on both the northbound and southbound lanes near Avenue 24. Officials say visibility at the time of the crash was 100 to 200 feet — the type of conditions CHP frequently describes as "sudden wall of white" events.
"Drivers were hitting fog so thick they couldn't see brake lights until it was too late," authorities said.
Dozens of drivers who escaped injury were taken by bus to the Tulare Ag Center for shelter and reunification. As of 1 p.m., Highway 99 remained fully closed, and officials said the shutdown could last well into the evening while officers investigate and tow trucks work through the tangled stretch of crumpled cars, SUVs, and big rigs.
Here's what to know about the tule fog blanketing California's Central Valley and the rash of accidents that fog has caused this season.
Highway 99 detours after tule fog crash in Central California
Both northbound and southbound Highway 99 lanes are closed in the Earlimart area near Avenue 24.
Detour - Northbound: Traffic is being diverted off at Cecil Avenue.
Detour - Southbound: Traffic is being diverted off at Avenue 48.
A season defined by fog: Communities shrouded since November
The Saturday, Jan. 31, disaster comes during one of the longest and most stubborntule fog seasonsthe Central Valley has seen in years. Since just before Thanksgiving, millions of Californians from Redding to Bakersfield have woken up under a milky, unmoving blanket of mist and fog, with the National Weather Service issuing near‑daily advisories.
Dense Fog Advisoriesremained in effect across wide swaths of the San Joaquin Valley on Jan. 30 and Jan. 31, including communities around Fresno, Visalia, Porterville, Delano and Bakersfield, where visibility repeatedly dropped below a quarter‑mile — and in some cases to mere feet.
NASA satellite imagery captured Dec. 9 shows the Valley covered by a continuous cloud of tule fog stretching more than 300 miles, the result of "perfect" atmospheric conditions that began forming around Nov. 24 and have persisted through late January.
Residents say this year's fog stands apart.
"Never lasted this long in my 57 years here," Greg Clark of Redding told the Record Searchlight.
Meteorologists attribute the unusually persistent layer to a stagnant high‑pressure system that has trapped cold, moisture‑rich air close to the ground, preventing the daily "burn‑off" that often clears the fog by mid‑morning.
Other recent fog‑related crashes across Central Valley
The Jan. 31 pileup is the largest so far this winter — but not the only one.
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Law enforcement agencies say they've responded to dozens of fog‑related collisions in January alone, especially during the early‑morning commute.
Notable incidents this month around Central Valley include:
A 17‑vehicle collision in Fresno County on Jan. 12 that killed a 61‑year‑old man after visibility plunged to 10–15 feet along Highway 99.
Multiple crashes along Interstate 5 from Kern County north through the Valley, where zero‑visibility conditions have led to "very high transportation risk," according to the National Weather Service.
Commercial truck collisions on Highways 43 and 58 in Fresno and Kings counties in mid‑January, including a fatal crash near Highway 99 and Clovis Avenue.
Reduced visibility along I‑80 and surrounding roadways in the Sacramento Valley, where fog has repeatedly settled overnight near river basins and agricultural corridors.
CHP officials say the pattern is clear: sudden, severe visibility drops, drivers traveling too fast for conditions, and people exiting their vehicles on fog‑cloaked roadways — an extremely dangerous combination.
What is tule fog and why is it so dangerous?
Tule fog is a form of radiation fog, forming when moist ground, cool nights, clear skies, and calm winds combine — conditions common in the Central Valley from November through February.
What made the fog on Jan. 31 particularly hazardous, according to forecasters:
High pressure kept fog pinned to the surface
Winds stayed relatively still overnight
Overnight cooling deepened the atmospheric "lid," preventing dispersion
Visibility changed from ¼‑mile to a few dozen feet within seconds
"It's the classic tule fog setup," said NWS meteorologist Eric Kurth. "A big bowl of mist."
Safety Tips: How to drive in tule fog
For millions of Valley residents, avoiding fog entirely isn't always an option. But safety agencies say the right habits can save lives.
If you must drive:
Slow down — way down.Expect travel times to double or triple in heavy fog.
Use low‑beam headlights. High beams reflect off water droplets and make visibility worse.
Follow lane lines, not taillights.Looking at roadway markings helps maintain orientation.
Increase following distance dramatically.Give yourself several seconds of reaction time.
When will the fog lift?
Unfortunately, forecasters say the Central Valley's fog cycle isn't done.
Turn on hazard lights
Pull into a parking lot or rest area if possible
If no safe exit exists: pull as far onto the shoulder as possible, set the brake, keep hazard lights on, and remove your foot from the brake pedal to avoid attracting drivers who may mistake your lights for a lane marker
NOAA fog‑driving guide: https://www.weather.gov/safety/fog
Live CHP/Caltrans highway map: https://quickmap.dot.ca.gov
A stretch of mild, mostly dry weather with mid‑60s highs and mid‑40s lows is expected through the weekend. Conditions may improve slightly by late next week as temperatures warm into the upper 60s — but unless a stronger storm system disrupts the stagnant air mass, tule fog is likely to continue forming overnight and during early‑morning hours.
This article originally appeared on Visalia Times-Delta:Highway 99 closed after 150‑vehicle pileup in tule fog near Earlimart
