Northern California continues to be inundated by record-breaking floodwaters Thursday after the Russian River crested at its highest level in 25 years late Wednesday. More than 2,000 homes and businesses have been damaged by the flooding.

Both Guerneville and neighboring Monte Rio were completely cut off by the overflowing river, and were described as "islands" by local officials. Ahead of the flooding, nearly 4,000 residents were ordered to evacuate the Guerneville area, but local authorities believe that only about half did so. The Sonoma County Board of Supervisors declared a local emergency, and the Los Angeles Times reported that authorities warned that those who didn't evacuate could be stuck in their homes for days.

(MORE: Northern California Flooding Cuts off Towns, Damages 2,000+ Homes)

Parts of Sonoma County received more than a foot of rain, with the highest totals surpassing 20 inches.

Sonoma County Sheriff Mark Essick told the Press Democrat that officials had completed about 40 rescues by late Wednesday. According to the AP, no injuries were reported in the Guerneville area.

Many Sonoma County schools were closed Wednesday and again Thursday due to the flooding. The Russian River wasn't expected to recede again until Thursday night.