Severe thunderstorms caused damage across the Washington, DC, region Saturday, with downed trees and power lines and suspended service on parts of the Metro train system.

DC Fire EMS said on its Twitter account it is responding to multiple emergency calls for trees and wires down, and is prioritizing calls for trees on vehicles or structural damage.

The agency also said crews are responding to a vessel taking on water in the Potomac River, and boats adrift in the Georgetown area.

Across the country, more than 100 million people are under heat alerts, according to the National Weather Service. Most are set to expire Saturday night.

The Washington Metropolitan Area Transit Agency has suspended service on a portion of the Red Line due to a downed tree, while other stations are being bypassed due to power outages, according to its Twitter feed.

The area's utility provider, Pepco, reports some 64,000 power outages on its website.

In nearby Arlington County in Virginia, the fire department said on Twitter it is experiencing "significant increase in call volume" and responses would be delayed.

The National Weather Service had issued a severe thunderstorm warning for portions of the area and warned of 80 mph winds.