(CNN) -- Millions of people across nine states were left without power Saturday to deal with thermostat-popping temperatures after fierce storms pounded parts of the Midwest and Atlantic Seaboard.

Six people were killed in Virginia, crushed by felled trees, said Gov. Bob McDonnell, who declared an state of emergency in the state.

The storms moved east Friday from Indiana through Ohio and into West Virginia and the nation's capital.

In all, 3.6 million homes were without power Saturday morning; nearly 1 million in Virginia alone. The power outages and debris littering roads led to traffic disruptions and other headaches.

Amtrak service between Washington and Philadelphia was expected to be restored by noon Saturday after the storm downed trees and wires across tracks.

In the nation's capital, many intersections were without traffic lights Saturday.

The aftermath of the storm was compounded Saturday by a forecast of another sweltering summer day.

One in three Americans were baking Saturday in an area of nearly 600,000 square miles sizzling under the sun.

Temperatures tipped the 100-degree mark in several cities Friday, including St. Louis, Richmond, Nashville, Washington and Atlanta, the National Weather Service said.

In many places, it felt much hotter than the thermostat reading.

"If you don't have a good pair of boots, it'll burn clear through to your feet," said roofer Zach Bruner in Evansville, Indiana, where he said the 103-degree temperatures were spiking to 130 on the job site.

The bad news? Relief is nowhere in sight as the extreme heat is expected to continue through the weekend.

In storm-affected areas, many people had no electricity to run fans, air-conditioning and refrigerators. Even in places where power was not disrupted, people with no air-conditioning were advised to spend the day in a library or a cooling center to avoid heat exhaustion.

Atlanta opened five cooling centers in anticipation of another day of triple-digit heat.

Fueled by the high temperatures, the severe thunderstorms brought with them winds gusting to 80 miles per hour, the weather service said.

Saturday morning, the storm's fury was visible with downed trees and debris littering roads.

Catherine Estelle Ford of Scottsville, Virginia, died when a tree fell on her after she stepped out of her car and tried to make a phone call, according to the Albemarle County Police Department.

Five others died due to downed trees, according to the Virginia governor.

The Jackson County medical examiner in western Missouri is investigating three deaths that may be related to the heat, according to the Kansas City Health Department.

The National Weather Service issued an excessive heat warning through Sunday for eastern Missouri, including St. Louis, where temperatures are expected to soar up to 106 this weekend.

"Heat-related illness such as heat exhaustion or heat stroke are a real threat," the weather agency said. "This is especially true because of the longevity of this heat wave and the effects of extreme heat are cumulative."

In Memphis, where highs hit 105 degrees Friday, firefighters went door to door, checking on residents. Churches and faith-based institutions were also urged to ask people to check on their neighbors and relatives.

"Please, if you know of someone who doesn't have air conditioning or who might be struggling with the heat, just stop by and see how they are doing," Mayor A.C. Wharton Jr. said.

The weather service posted excessive heat warnings for 12 states, from Nebraska to New Jersey, with watches and advisories posted for at least six other states.

Baltimore Mayor Stephanie Rawlings-Blake activated the city's emergency operations to coordinate storm recovery operations. In West Virginia, Gov. Earl Ray Tomblin declared a state of emergency for the entire state after the powerful storms.

And at the Congressional Country Club in Maryland, play was suspended in the third round of the AT&T National as trees and tents came crashing down and the PGA venue was left without power.

The third round was slated to begin at 7:10 a.m. Saturday, but the course lay eerily empty as the tournament announced it was closed to all fans in the interest of safety.

The tournament website simply said: "Stay tuned for details."

CNN's Moni Basu, Fabi Rodriguez, Nick Valencia, Melissa Abbey and Jake Carpenter contributed to this report.