The crash happened before 11 pm on the northbound 99 near Merced Street.
The California Highway Patrol (CHP) says the driver of the sedan pulled over because of a flat tire, and stepped out of the car.
Moments later, a big rig collided with her vehicle, pushing it nearly 700 feet into the third lane.
Both the sedan and semi caught fire and are completely destroyed.
Despite the heavy damage, no one was hurt.
Crews are working to reopen all lanes soon as they remove the wreckage.