The atmospheric river caused the flood. “It came really fast.”

On Friday, a so-called atmospheric river reached the northern areas of California, dumping huge amounts of rain. This is the term for a long band of moisture that forms in the atmosphere over warm ocean waters and, when moving over land, can cause heavy rainfall and snowfall.

Many roads and properties were flooded in Sonoma County north of San Francisco. The water was over a meter high in some places. Some roads are still impassable.

Earlier, about 150 people living near the Russian River, which was at risk of flooding, were evacuated as a preventive measure, also due to heavy snowfall in mountainous areas.

Those who did not escape from high water helped others. – Some people asked for help on social media, wanting to get to the other side or to the store. I thought I had all day and a boat, so I could help, said Ben Conte from Forestville. – It came really fast. All low-lying areas were hit quite hard by the flood, he said.

“I was packing my things and watching the water get closer,” said Shannon Defoor of Forestville, Sonoma County. As she said, it was not the first such sudden flood in her life, but “this time the water appeared extremely quickly.”

“It was record rainfall for three days,” said Matt Windrem of the local fire department. He added that he did not remember similar floods in this area.

Forecasters warn of the risk of landslides in the areas most affected by the downpours. In some places, previous downpours had passed just a few days earlier.

Earlier this week, a cyclone hit the northwestern United States. This is a rapidly developing low-pressure system in which the pressure may drop by at least 24 hectopascals per day. These types of phenomena bring intense rainfall with strong winds. There was extensive damage in California, as well as in the states of Washington and Oregon. Two people died.