The history of the Central Valley Tule Fog

If you lived in the Central Valley of California some 20-30 years ago, you likely remember an unpleasant winter weather pattern called “Tule Fog.” Every year, it would appear out of the blue and stick around for days or even weeks. 

No ordinary mist, this was a thick fog, capable of reducing visibility down to feet or even inches. It was the cause of many multiple vehicle, pile-up accidents on the area freeways – at times involving up to a hundred cars.  

Heading into the 2021 winter, can we expect to witness the Tule Fog weather phenomena? Chances are increasingly slim. Slowly over the past 10-15 years, Tule Fog has become less common. 

The future of the fog

Formation of fog requires three elements; cooling temperatures, water vapor, and condensation nuclei: a speck of dust or other compound for the water vapor to condense upon when it cools. People have hypothesized that the less frequent Tule Fog is due to the drought conditions that have plagued California of late. Not enough water to saturate the ground and allow for proper evaporation to take place. 

Another theory has to do with the overwhelming development of the valley. 1000s of acres of open fields and ranchland have been rapidly converted into shopping centers, new homes, and paved streets, none of which are surfaces that trap and hold moisture like soil does. 

In the final estimation, U.C. Berkeley researchers have discovered that neither possible explanation “holds water”. The real reason is cleaner air. Thanks to the Clean Air Act, California’s Central Valley has far less pollution particles in the air for water vapor to cling to, resulting in nothing more than Tule Mist. And thankfully, fewer car accidents!

Reasons to continue loving the Central Valley

Along with cleaner air, life in the Central Valley includes mild winters, affordable housing, and amazing landscape. Between the rivers, lakes, 100s of miles of bike trails and proximity to Lake Tahoe ski resorts and famous National Parks like Yosemite, you’ll never run out of new things to discover.

Like the beautiful area of California where it takes place, Del Rio, my latest book set in the Central Valley, has just as many twists and turns and exciting adventures around every corner. 

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