Hours after a massive traffic jam shut down Interstate 99 near Earlimart in dense tule fog, the southbound lanes were fully reopened and Caltrans began directing northbound traffic on Cecil Avenue beginning at 2:30 p.m. Saturday.
The crash, which occurred in near-zero visibility shortly after 8:15 a.m., sent at least 10 people to local hospitals and left many drivers stranded as crews worked to clear the wreckage that spanned both sides of the highway.
The California Highway Patrol began receiving calls shortly after 8:15 a.m. reporting multiple collisions in both 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 the CHP frequently describes as “sudden wall of white” events.
Initial reports suggested the pileup involved 150 vehicles, but authorities later revised the number to 59 after a close examination of the wreckage. As of 3:00 p.m. Saturday, no deaths and only moderate injuries had been reported.
“Drivers were hitting fog so thick they couldn’t see their brake lights until it was too late,” authorities said.
Tow trucks, investigators and Caltrans crews spent much of the morning and early afternoon clearing the wreckage from both sides of the highway. While traffic has begun to move again, the CHP is warning of significant delays, particularly northbound, where escorts remain in place and cleanup is underway.
Here’s what you need to know about the tule fog blanketing California’s Central Valley and the rash of accidents the fog has caused this season.
This is breaking news. Check back for more details.
A Season Defined by Fog: Valley Communities Shrouded in November
Saturday’s disaster comes during one of the longest and most stubborn tule fog seasons the Central Valley has seen in years. Just before Thanksgiving, millions of Californians from Redding to Bakersfield awoke under a milky, motionless blanket of fog and mist, with the National Weather Service issuing near-daily advisories.
Related: Tule fog triggers 43-vehicle pileup on Highway 58 near Bakersfield
Dense fog advisories remained in effect for large areas of the San Joaquin Valley Friday and into Saturday morning, including communities around Fresno, Visalia, Porterville, Delano and Bakersfield, where visibility repeatedly dropped below a quarter mile — and in some cases to just feet.
Related: The Tule Fog blankets California’s Central Valley with no relief in sight
NASA satellite images captured Dec. 9 show the Valley shrouded in a continuous cloud of tule fog stretching more than 300 miles, the result of “perfect” atmospheric conditions that began to form around Nov. 24 and persisted through late January.
Residents say this year’s fog is staying away.
“It’s never taken 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 trapped cool, moisture-rich air close to the ground, preventing the daily “burn-off” that often cleared the fog by mid-morning.
Other recent fog-related accidents in the Central Valley
Saturday’s crowd is the biggest so far this winter – but not the only one.
Law enforcement agencies say they responded to dozens of fog-related collisions in January alone, particularly during the early commute.
Notable incidents this month include:
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A 17-vehicle collision in Fresno County on Jan. 12 that killed a 61-year-old man after visibility dropped to 10-15 feet along the 99 Freeway.
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Multiple accidents along Interstate 5 from Kern County north through the Valley, where zero-visibility conditions led to a “very high risk for transportation,” according to the National Weather Service.
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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.
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Low visibility along I-80 and surrounding roads in the Sacramento Valley, where fog settled repeatedly overnight near river basins and agricultural corridors.
CHP officials say the pattern is clear: sudden drops in visibility, drivers traveling too fast for the conditions and people getting out of their vehicles on fog-shrouded roads — an extremely dangerous combination.
Why Tule Fog is so dangerous
Tule fog is a form of radiation fog that forms when wet ground, cool nights, clear skies, and calm winds combine — conditions common in the Central Valley from November to February.
What made today’s fog particularly dangerous, according to forecasters:
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The high pressure kept the fog attached to the surface
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Winds remained relatively calm overnight
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Overnight cooling deepened the atmospheric “cap”, preventing dispersal
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Visibility changed from ¼ mile to several tens of meters in seconds
“It’s the classic tule fog setup,” said NWS meteorologist Eric Kurth. “A big bowl of fog.”
Safety Tips: How to Drive in Tule Fog
For millions of Valley residents, avoiding the fog completely isn’t always an option. But safety agencies say the right habits can save lives.
If you must drive:
Slow down — down. Expect travel time to double or triple in heavy fog.
Use low beam headlights. High beams reflect water droplets and worsen visibility.
Follow the lane lines, not the traffic lights. Looking at road markings helps to keep one’s bearings.
Dramatically increase tracking distance. Give yourself a few seconds of reaction time.
If driving becomes too unsafe:
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Pull into a parking lot or rest area if possible
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If there is no safe exit: pull over to the shoulder as far as possible, apply the brakes, keep your hazard lights on and take your foot off the brake pedal to avoid attracting drivers who may mistake your lights for a lane marker.
When will the fog lift?
Unfortunately, forecasters say the Central Valley fog cycle isn’t over.
Conditions may improve slightly by the end of next week as temperatures warm into the 60s – but unless a stronger storm system disrupts the stagnant air mass, tule fog is likely to continue to form overnight and into the morning hours.
This article originally appeared on the Visalia Times-Delta: Interstate 99 closed after vehicles pile up in tule fog near Earlimart