Tornadogenesis can occur because of a supercell thunderstorm, a waterspout, a landspout, or a fire whirl, and can happen in any month of the year.
In July 2004, a twister touched down in Sequoia National Park at an altitude of around 12,156 ft (3,705 m), making it the highest elevation for a confirmed tornado in the United States.
In the United States, tornadoes develop less frequently west of the Rocky Mountains as compared to the rest of the continent.
[5] On rare occasion, tornadoes can originate from supercells, which are more similar in nature to twisters across the Midwestern United States.
[6] Because of their irregular and short-lived nature, the San Diego National Weather Service considers it "nearly impossible to forecast a Southern California tornado before it touches down."
[5] The location of the mountains relative to the coastline creates the favorable conditions for tornadogenesis in the Los Angeles Area.
[2] In the Central Valley, tornadoes can form when the winds from a trough are perpendicular to the coastal range of mountains, bringing onshore moisture from the San Francisco area to the Sierra Nevadas.
There have never been any recorded tornadoes in Alpine, Amador, Lake, Modoc, Mono, Napa, Plumas, Sierra, or Trinity counties.