Emergency officials voluntarily evacuated 650 homes in the low-lying communities of Monte Rio and Guerneville in Sonoma County as the Russian River continued to rise Sunday evening. The river is expected to peak at noon on Monday and will probably remain at or above flood levels through Tuesday morning, officials said.

Authorities said nearly 400 homes in Reno and other areas of Washoe County, Nev., were voluntarily evacuated Sunday due to widespread flooding that is expected to worsen overnight and into Monday.

Officials expect the Truckee River to crest 1 to 2  feet above flood stage by 10 p.m. on Sunday in Reno and reach its highest level at 6 feet above flood stage by 7 a.m. Monday in neighboring Sparks.

One Reno neighborhood was placed under voluntary evacuation orders because of a storm-related sewage station failure that poses a health hazard.