Over the past few days, a layer of fog and low clouds has slowly been expanding through the Valley and into the lower Foothills.

This persistent gloomy weather has a colloquial name in the Central Valley: Tule fog.

It's a common feature of winter weather in California, forming during the calm, cool nights that follow a stretch of rainy days.

Tule fog can lead to dangerously poor visibility for drivers, especially on freeways where traffic flows much faster.

In December of 1997, Tule Fog was blamed for a quarter-mile-long fiery crash on Interstate 5 in Sacramento County.

One experienced truck driver recalls his anxiety that day.

"I’ve been driving 15 years and today, it’s like my first day in this truck. I’m nervous, y’know," he said.

Five people were killed in that chain reaction cr

See Full Page