Millions across the mid-Atlantic region sweltered Saturday in the aftermath of violent storms that pummeled the eastern U.S. with high winds and downed trees, killing at least 13 people and leaving 3 million without power during a triple-digit heat wave.

Power officials said the outages wouldn’t be repaired for several days to a week, likening the damage to a serious hurricane. Emergencies were declared in Maryland, West Virginia, Ohio, the District of Columbia and Virginia, where Gov. Bob McDonnell said the state had its largest non-hurricane outage in history, as more storms threatened. “This is a very dangerous situation,” the governor said.

In some Virginia suburbs of Washington, emergency 911 call centers were out of service; residents were told to call local police and fire departments. Huge trees fell across streets in Washington, leaving cars crunched up next to them, and onto the fairway at the AT&T National golf tournament in Maryland. Cell phone and Internet service was spotty, gas stations shut down and residents were urged to conserve water until sewage plants returned to power.