California Governor Gavin Newsom Thursday declared a state of emergency for five counties in Northern California as a result of severe storms.

The governor's office said the emergency proclamation was issued for the counties of Amador, Glenn, Lake, Mendocino and Sonoma to help communities respond to and recover from dangerous flooding, mudslides and damage to critical infrastructure.

TV footage of local media showed torrential rains have flooded the Russian River in Sonoma County Wednesday, turning the town of Guerneville in western Sonoma into an "island," as the river reached its highest level of 14 meters in 25 years at night.

Thousands of residents from Guerneville and from two dozen other communities were evacuated from the flooded areas.

Newsom said multiple storms caused rivers to exceed flood stages, including the Russian River, "which has threatened homes and forced the evacuation of thousands of residents."

He said he has directed officials to formally request immediate assistance through the Federal Highway Administration's Emergency Relief Program and the Office of Emergency Services to provide assistance to local governments.

The state of emergency came after a significant atmospheric river storm system swept across California, which began on Feb. 25 and brought substantial precipitation, snowfall, high winds, mud and debris flows, and dangerous flooding.

Newsom previously declared an emergency for 21 counties across the state due to widespread damage and flooding from heavy storms on Feb. 21.