One man was clinging to a tree and had to be rescued by a sheriff's helicopter. Four other people sought higher ground on an island and were rescued by crews from the Riverside Fire Department.
Rain turned to heavy snow in higher elevations, including rural eastern Nevada's Lincoln County.
Deputies there were trying to help people after 50 of 60 cars got stranded overnight in "a long stretch of absolutely nothing," according to dispatcher Shannon Miller.
No injuries were reported, Miller said, but U.S. 93 was closed south of U.S. 6 in Ely.
Snow in higher elevations in New Mexico and Arizona, including up to 4 inches around Flagstaff, Ariz., created dangerous road conditions and prompted some schools to delay opening Friday.