Tule fog

Tule fog forms from late fall through early spring (California's winter season) after the first significant rainfall.

The nights are longer in the winter months, which allows an extended period of ground cooling, and thereby a pronounced temperature inversion at a low altitude.

[2] In California, tule fog can extend from Bakersfield to Red Bluff, covering a distance of over 650 kilometres (400 mi).

Tule fog is a low cloud, usually below 2,000 feet (600 m) in altitude and can be seen from above by driving up into the foothills of the Sierra Nevada to the east or the Coast Ranges to the west.

In one such accident on Interstate 5 near Elk Grove south of Sacramento, 25 cars and nine big-rig trucks collided inside a fog bank on December 12, 1997.

On the morning of November 3, 2007, heavy tule fog caused a massive pile-up that included 108 passenger vehicles and 18 big-rig trucks on northbound State Route 99 between Fowler and Fresno.

Besides water droplets, the composition of tule fog in the San Joaquin and Sacramento valleys includes ammonia, nitrate and sulfate concentrations.

Depending on the region within the California Central Valley, the composition of tule fog can vary in element or ion concentrations.