Which states affected

• NEW: 12 people are killed, including two boys in New Jersey
• At least 3.2 million homes remain without power
• More storms could move through the region Saturday night

(CNN) -- Millions of people were sweltering Saturday in record-breaking heat in the wake of deadly storms that ripped across the Midwest and Mid-Atlantic.

At least 12 people were killed and three states -- Virginia, West Virginia and Ohio -- declared states of emergency. As of Saturday evening, more than 3.1 million homes remained without power, down from 3.7 million earlier.

America is having a heat wave

A look at the latest developments in the most-affected states:

3 states declare emergencies as heat, deadly storms bring misery to millions

VIRGINIA

Virginia was among the hardest-hit states, both in terms of fatalities and the number of power outages. Close to 800,000 customers remained without power Saturday evening.

Catherine Estelle Ford, of Scottsville, 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 in Virginia due to downed trees, according to the governor, who declared a state of emergency in response to the severe weather.

MARYLAND

A 71-year-old woman in Montgomery County was crushed by a tree that crashed onto her home, according to Lucille Baur, a public information officer.

Baltimore Mayor Stephanie Rawlings-Blake activated the city's emergency operations to coordinate storm recovery operations.

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

By Saturday afternoon, the course was still closed to fans and volunteers even after play resumed. Across the state, close to 800,000 customers remained without power Saturday evening.

DISTRICT OF COLUMBIA

A man and his wife were electrocuted when they stepped outside to check on downed trees and power lines, said police spokesman Araz Alali. The man was killed and his wife was is in critical condition with burns. She is expected to survive, Alali said.

In the nation's capital, 19 intersections were without traffic lights at one point Saturday.

Joseph Rigby, president of the electric company Pepco, said it could be a week before power is fully back up in some areas of Washington.

Close to 64,000 customers were without power Saturday evening.

Storm leaves much of D.C. without power, sweltering

MISSOURI

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

KENTUCKY

A 30-year-old man was working to clear a road of fallen limbs when a nearby tree fell and killed him, according to Robert Gayheart, Clark County coroner.

More than 36,000 customers remained without power in the state Saturday evening.

WEST VIRGINIA

In West Virginia, Gov. Earl Ray Tomblin declared a state of emergency for the entire state after the powerful storms. More than 600,000 people remained without power Saturday evening.

NEW JERSEY

Two boys, ages 7 and 2, were killed in Parvin State Park in Salem County when a pine tree snapped and fell on their campsite, the New Jersey Department of Environmental Protection said in a news release.

The boys were cousins from Millville. When the storm began, their families had huddled together in a single tent that ended up being crushed by the tree.

Close to 150,000 customers were without power Saturday evening.

OHIO

In eastern Ohio, 70-year-old Marsha Reutter was in her barn with her husband, feeding farm animals, when strong winds blew through and caused the barn to collapse, said Jeff Jadwin, deputy emergency management director for Muskingum County.

Her husband was able to pull himself out, but Reutter died at the scene, according to Jadwin.

The governor declared a state of emergency, while close to 650,000 customers across Ohio were still without power Saturday evening.

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CNN's Maggie Schneider contributed to this report.