By allowing ads to appear on this site, you support the local businesses who, in turn, support great journalism.
Celebrating 2 unique Central Valley creations
During a previous Tule Fog Fete, Columbia College biology instructor Guy Van Cleave led one of the guided tours. - photo by HIME ROMERO


• WHAT: Tule Fog Fete
• WHEN: Sunday, March 6, from 11 a.m. to 3 p.m.
• WHERE: Caswell State Memorial Park at the southern end of Austin Road.
• ADMISSION TO PARK:  $5 per person or $15 per carload
• MORE INFO: Contact Great Valley Museum at 575-6196

Tule fog - that thick pea soup-like concoction that permeates from the ground - is as unique to the Central Valley as Caswell State Park.

You can celebrate both this Sunday during the annual Tule Fog Fete from 11 a.m. to 3 p.m. at Caswell Memorial State Park located at the southern end of Austin Road along the edge of the Stanislaus River.

The family-oriented festival features bluegrass music; guided nature walks; live, native animals; educational science and hands-on nature stations, storytelling and crafts. Hot food and drinks will be available for purchase. Staged as a fundraiser for the Great Valley Museum of Modesto Junior College, it is an ideal way to celebrate the end of the fog season and the approach of spring as the largest remaining stand of rare riparian and oak woodland prepares to come out of its winter slumber. Riparian woodlands once covered much of the valley. Today, almost 98 percent of what existed in 1850 is gone.

The annual event at Caswell State Park is as mellow as the setting.

Admission is $5 per person or $15 per carload.

Many who first arrive in the Central Valley believe the fog here all rolls in from the ocean or from bodies of water such as the Delta. Some of it does but tule fog is a thick ground fog that forms during the rainy season from late fall through winter. Weather experts say you’ll only find it from Nov. 1 to March 31. That’s the time the right conditions can exist to create tule fog.

It requires high relative humidity that can come after a heavy rain, calm winds, plus rapid nighttime cooling. This creates temperature inversion at a low level thanks to cold mountain air flowing into the valley at night. This combines with warmer air passing at higher attitudes that can trap the fog for days or even weeks. In 1991 there were parts of the Central Valley that was socked in with tule fog for more than 20 consecutive days keeping temperatures in the 40s while up in the foothills around Auburn and Sonora they were in the high 60s.

Sometimes the radiation fog has a light drizzle.

The visibility is extremely low going from 600 feet down to 10 feet and even near zero.

The fog forms below 1,000 feet and can be seen driving into the Sierra foothills or over the Altamont Pass

The fog is named tule grass or wetlands found in the valley.