The U.S. National Weather Service on Saturday issued new warnings against another day of record-breaking heat in mainly eastern U.S. following overnight thunderstorms that rendered massive damages across the region.

"High temperatures this afternoon will exceed 100 degrees Fahrenheit (38 degrees Celsius) across the mid/lower Mississippi River Valley eastward through the Mid-Atlantic and Southeast today. In fact, some locations are expected to break record high temperatures for late June," the NWS said in its warnings.

The greatest risk will stretch from southern Ohio into Maryland and northern Virginia, where the residents were urged to "remain alert to the latest forecasts and warnings from the NWS," the NWS said, adding the temperature could reach from 105 to 115 degrees Fahrenheit (40.5 - 46 degrees Celsius).

Temperatures climbed above 100 degrees Fahrenheit (37.7 degrees Celsius) on Friday in St. Louis, Richmond in Virginia, Nashville in North Carolina, and Atlanta in Georgia. In Washington D.C., the U.S. capital, the highest temperature hit 105 degrees Fahrenheit ( 40.5 degrees Celsius), which broke the previous record in 1934, the NWS said.

At least five people were reportedly killed in the thunderstorms Friday night, including two in Virginia, two in New Jersey and another in Maryland.

More than 4 million people in mainly eastern U.S. were left without power Saturday after severe thunderstorms struck middle and eastern U.S. overnight as result of the sweltering heat wave.

Wind gusts reached 70 to 80 miles (112-128 kms) per hour during Friday night's violent storm which pounded mainly northern Virginia, as well as neighboring regions of Washington, D.C., Maryland, North Carolina, New Jersey, Indiana, Ohio and West Virginia, after the hottest weekend of the year.

Damage was also reported to the Washington, D.C. subway cars by falling trees, according to local media reports. There were also multiple reports of parked cars hit by falling trees or branches.

Internet connection, local and cell phone services were cut on Saturday at Xinhua Washington Bureau in Arlington, Virginia, though it was not affected by the power outage.

West Virginia has declared a state of emergency as more than 500,000 customers in 27 counties were affected by power outages.

In Baltimore of Maryland, the municipal government activated emergency operations to coordinate operations for storm recovery.

In Memphis, Tennessee, where highs hit 105 degrees Fahrenheit ( 40.5 degrees Celsius) on Friday, firefighters went door to door to check on residents, local media reported.