A dangerous weekend weather system killed at least 18 people in the U.S. South, with Georgia officials reporting more than a dozen deaths on Sunday after severe thunderstorms and tornadoes buffeted several states.

Seven people died in Cook County, Georgia, state emergency managers said, with a mobile home park particularly hard hit, according to reports. Photos showed collapsed buildings, destroyed rooftops, toppled trees and debris-littered fields.

Georgia Governor Nathan Deal declared an emergency for seven counties in the south-central part of the state, warning that dangerous conditions persisted as wind and flood warnings remained in effect for much of the state early on Monday.

“I urge all Georgians to exercise caution and vigilance in order to remain safe and prevent further loss of life or injuries,” Deal said in a news release.

First Baptist Church Adel, located in the Cook County seat near the Florida-Georgia state line, was sheltering more than 50 people, said pastor Bill Marlette, who had just helped inform a family that two of their relatives were among the dead.

“There’s a lot of hurting people right now,” he said in a telephone interview. “There’s just a sense of shock.”

The storms in Georgia, which killed 14 people, followed a predawn tornado in Mississippi on Saturday that killed four. Severe weather also injured more than 50 others and damaged about 480 homes in Mississippi.

A few storms continued to threatened coastal areas in Georgia on Sunday night, said Mark McKinnon, a spokesman for the Georgia Emergency Management and Homeland Security Agency.

The National Weather Service issued a flash flood warning for Rome and Calhoun until 3.30 a.m. EST, advising residents to move to higher ground.

The system prompted forecasters to issue a rare “high risk” warning of severe storms threatening parts of southern Georgia, north and central Florida and Alabama on Sunday, the first such warning since 2014. South Carolina could also see severe weather.

In Alabama, some 29,000 power outages were reported as of Sunday afternoon, Alabama Power said. Several thousand had also been without power in Mississippi.

The severe weather was expected to last through Sunday night.

As the system churned up the East coast, emergency management officials warned New York City residents to brace for winds of up to 70 mph through Monday night, with several inches of drenching rains. Flood advisories and watches were issued for four of the city’s five boroughs.

On the west coast, heavy rains from a separate system drenched parts of Southern California, with forecasters warning the storm could be the most severe in several years.

(Additional reporting by Frank McGurty and Chris Michaud in New York, David Beasley in Atlanta and Sharon Bernstein in Sacramento, Calif.)