Highway 99 runs through one of California’s most dangerous winter driving environments. Between November and February, dense tule fog settles across the San Joaquin Valley, reducing visibility along major freight routes connecting Bakersfield, Delano, Visalia, Tulare, and Fresno.
The danger becomes clear in major pileups. On January 31, 2026, 59 vehicles collided along Highway 99 near Avenue 24, north of Delano. California Highway Patrol (CHP) officials reported visibility of just 100 to 200 feet. Ten people were hospitalized, and both directions of the highway closed for several hours.
The incident followed a history of serious fog-related crashes on the same corridor. Understanding the pattern requires examining visibility, vehicle speed, commercial truck traffic, and the legal duties drivers retain during poor weather.
Findings From Highway 99 Fog Crashes
- A January 31, 2026, pileup near Delano involved 59 vehicles and sent 10 people to hospitals.
- CHP reported visibility between 100 and 200 feet during the collision.
- A November 2007 fog pileup south of Fresno killed two people and injured dozens.
- Sudden visibility changes, excessive speed for conditions, and commercial truck involvement increase the complexity of multi-vehicle collisions.
- California’s basic speed law requires drivers to adjust their speed for weather, visibility, traffic, and road conditions.
These incidents show why a posted speed limit does not establish a safe speed during dense fog.
What Is Tule Fog?
Tule fog is a type of radiation fog that forms near the ground when moist air cools overnight. The San Joaquin Valley provides favorable conditions because surrounding mountains restrict air movement, while agricultural land and winter rainfall supply moisture.
The fog is most common during late fall and winter, especially from November through February.
Unlike ordinary morning haze, dense tule fog sharply reduces the distance drivers see ahead. Visibility changes across short distances. A driver traveling through clear conditions suddenly enters a fog bank with only a few hundred feet of roadway visible.
The National Weather Service identifies dense fog as a recurring Central Valley hazard. Its uneven distribution makes highway travel particularly dangerous because drivers encounter different visibility conditions along the same route.
Major Highway 99 Fog Pileups
Two major crashes illustrate the recurring danger.
| Date | Location | Vehicles involved | Reported outcome |
| November 3, 2007 | Highway 99 south of Fresno | Approximately 100; reports range from 86 to 108 | 2 fatalities, dozens injured |
| January 31, 2026 | Avenue 24, north of Delano | 59 | 10 hospitalized; both directions closed for several hours |
The 2007 crash involved passenger vehicles and commercial trucks across a lengthy stretch of northbound Highway 99. Contemporary reporting identified 18 big rigs among the vehicles involved.
The 2026 incident unfolded across both directions of the highway near the Tulare-Kern county line. Initial reports suggested a much larger number of vehicles before CHP confirmed 59.
The crashes occurred nearly two decades apart, but both involved the same underlying hazard: drivers encountering sharply reduced visibility while traveling on a high-speed freight corridor.
What Causes Chain-Reaction Crashes in Tule Fog?
Three conditions explain much of the danger.
1. Speed Differences Between Vehicles
A driver entering dense fog at highway speed approaches slower traffic with less time to react.
At 65 mph, a vehicle travels approximately 95 feet every second. At that speed, 200 feet of visibility represents just over two seconds of travel before accounting for reaction time or braking distance.
That calculation explains why sudden fog banks create serious collision risks.
The first impact blocks a lane. Following drivers encounter stopped vehicles before they have enough distance to respond. Additional collisions develop behind the original crash.
2. Vehicles Without Headlights
Daytime fog creates a visibility problem that automatic headlights do not always address.
Some automatic systems rely on ambient light rather than visibility distance. Bright daylight above the fog leaves those systems inactive.
Following the January 2026 crash, Tulare County officials emphasized manually activating headlights.
Low beams improve vehicle visibility without the glare produced by high beams reflecting off fog droplets.
3. Commercial Truck Traffic
Highway 99 serves agricultural producers, distribution centers, and freight operations throughout the Central Valley.
Loaded tractor-trailers require substantial stopping distances. Their size and weight also complicate collisions involving multiple smaller vehicles.
A truck entering an existing pileup introduces additional questions about following distance, driver response, braking, maintenance, and commercial carrier responsibility.
Truck involvement does not automatically establish negligence. Investigators must determine what each driver and company did before the collision.
Who Is Liable for a Highway 99 Pileup Caused by Tule Fog?
Drivers remain responsible for operating at a reasonable speed despite fog. California Vehicle Code Section 22350 requires motorists to consider visibility, traffic, weather, and road conditions. In a chain-reaction collision, liability depends on each driver’s conduct, the sequence of impacts, and whether that conduct contributed to the injuries.
Fog itself does not excuse negligent driving.
California follows pure comparative negligence. Multiple drivers share responsibility when the evidence establishes that their separate actions contributed to the crash.
Consider a hypothetical four-vehicle collision:
A driver enters fog without reducing speed and strikes stopped traffic. A second driver follows too closely and hits the first vehicle. A third driver brakes in time but is struck from behind.
Investigators must determine each impact’s timing and cause. The fact that all four vehicles appear in the same pileup does not establish equal responsibility.
California Civil Code Section 1431.2 also distinguishes responsibility for noneconomic damages, which generally follows each defendant’s percentage of fault.
This makes accurate fault allocation especially important in major Highway 99 collisions.
How Do Investigators Determine Fault in a 59-Vehicle Crash?
A major pileup requires reconstructing several collisions rather than treating the event as one impact. Investigators must establish which vehicle triggered the first collision, how subsequent impacts occurred, and whether individual drivers had enough time and distance to react.
CHP reports document initial observations, roadway conditions, vehicle positions, and witness accounts. Investigators compare those findings with physical and electronic evidence.
Important records include:
- Vehicle damage patterns: Identify contact points and help establish the sequence of impacts.
- Event data recorders: Provide recorded information about vehicle speed, braking, and other available parameters.
- Dashcam footage: Shows traffic movement and visibility before impact.
- Witness statements: Help establish the timing and sequence of collisions.
- Commercial truck records: Document driving hours, inspections, maintenance, and dispatch activity.
Evidence preservation becomes critical when dozens of vehicles and insurance companies are involved. Damaged vehicles are eventually repaired, sold, or salvaged, while electronic recordings face routine deletion.
Commercial truck involvement adds another layer. The motor carrier, maintenance contractor, and equipment owner hold different records that help establish whether driver conduct, mechanical problems, or company practices contributed to the collision.
For injured motorists, this creates a practical challenge: identifying every responsible party before the evidence needed to establish fault disappears. That is where regional injury firms such as May Firm fit into the investigation. With California car accident lawyers serving Visalia and other Central Valley communities, the firm handles vehicle accident claims involving disputed liability, multiple insurers, and commercial trucks. Its role in a Highway 99 collision is to pursue relevant records, examine the sequence of impacts, and establish which parties bear responsibility for the resulting injuries.
Why the Visalia Area Matters in Highway 99 Fog Investigations
Visalia sits along the Central Valley corridor connecting Fresno, Tulare, Delano, and Bakersfield. Residents regularly travel Highway 99 for employment, freight operations, and regional services.
The January 2026 pileup occurred in southern Tulare County, near the Kern County line. CHP personnel from the Visalia area participated in the emergency response.
For injured motorists, the location matters because collision reports, responding agencies, towing records, and witness information are tied to the area where the crash occurred.
A serious pileup also involves insurers representing drivers from different counties and commercial carriers operating across California.
That creates a practical reason to work with an injury firm familiar with the region. The May Firm maintains a Visalia office and handles vehicle accident claims throughout the Central Valley. Its Visalia car accident lawyers represent people injured in collisions involving disputed liability and multiple insurance companies.
In a Highway 99 pileup, the legal investigation begins with identifying the relevant CHP records, reconstructing the impacts, and preserving vehicle evidence. The location of the crash determines where much of that investigation starts.
What Should Drivers Do After a Highway 99 Fog Pileup?
Medical care comes first. Drivers should report injuries and follow emergency responders’ instructions before attempting to document the scene.
Once conditions are safe, photographs of vehicle damage, roadway positions, and surrounding conditions provide useful evidence.
Obtain the investigating agency’s report information and identify any available witnesses.
Retain medical records, repair estimates, towing receipts, and communications with insurance companies.
Do not assume that the driver immediately behind a damaged vehicle caused every injury. Earlier and later impacts require separate examination in a chain-reaction crash.
Commercial vehicle owners should also receive prompt notice to preserve relevant electronic and maintenance records.
How to Drive Highway 99 Safely During Tule Fog Season
Winter travel through the Central Valley requires preparation before entering the highway.
Check Caltrans QuickMap for closures, traffic incidents, and road conditions. Review National Weather Service dense fog advisories before early morning travel.
Turn on low-beam headlights manually when visibility drops. High beams create additional glare.
Reduce speed before entering a fog bank and increase following distance. Avoid abrupt braking when approaching slower traffic.
Never stop in an active travel lane simply because visibility deteriorates. Use a safe exit or designated stopping area when conditions permit.
Drivers who become involved in a collision should follow CHP instructions and avoid standing near moving traffic.
Highway 99 Tule Fog Crashes
When is tule fog season in California?
Tule fog occurs primarily from November through February. The Central Valley experiences its strongest events during cool, moist, calm winter conditions.
Why does Highway 99 have large fog pileups?
High traffic volumes, commercial trucks, highway speeds, and sudden visibility changes create conditions for chain-reaction collisions. The 2007 and 2026 crashes demonstrate the severity of those conditions.
Who pays for injuries in a multi-car pileup?
Liability depends on which drivers or other responsible parties caused or contributed to the collision. California’s comparative fault rules govern how responsibility affects compensation.
Is a driver automatically at fault for rear-ending another vehicle in fog?
No automatic conclusion replaces an investigation. Following distance, speed, roadway conditions, vehicle movement, and the sequence of impacts determine negligence and causation.
Does bad weather excuse a driver from liability?
No. California’s basic speed law requires motorists to adjust driving speed to existing weather and visibility conditions.
How long do injured drivers have to file a California accident lawsuit?
Most California personal injury lawsuits have a two-year filing period under Code of Civil Procedure Section 335.1. Government-related claims and other exceptions follow different deadlines.
The Lesson From Highway 99’s Fog Crash History
The November 2007 and January 2026 pileups show that tule fog remains a serious hazard along Highway 99.
Both incidents involved sudden visibility loss and numerous vehicles. The resulting investigations extend beyond weather conditions to driver speed, reaction time, commercial vehicle operation, and the order of collisions.
For Central Valley motorists, the most effective protection starts before entering dense fog: reduce speed, use low-beam headlights, and maintain enough distance to stop within the visible roadway.
For people injured in a pileup, establishing responsibility requires preserving evidence and examining each collision separately. The number of vehicles involved makes that investigation more demanding, not less important.
