Cessna Skyhawk (N73516)

A semi tractor trailer rig passing by on Interstate 5 (which is directly west of Runway 32-14 and is parallel to it) was almost flipped by the same blast of wind. The box was actually tipping over when the driver swerved his rig enough to bring his rig and the trailer back down on all sets of tires. I didn't see the initial instant when the crosswind hit the semi because I was snapping this Cessna just as it was about to touch down, but I did hear the squealing tires and a horn and I did hear the trailer bounce heavily back down on to the highway. I glanced over and the rig was shutting down and pulling off of the hammer lane side on to the middle median area. I didn't see any other vehicles in the immediate vicinity. After I clicked this Cessna on the go I looked over at the highway and the rig was crossing over the two lanes to the shoulder but there were no other vehicles involved in the incident that I could see.
That portion of I-5 is known for having extreme crosswinds and there are highway signs posted along I-5 warning of such winds.