A boy plays in a water fountain in Washington on Sunday, July 1, amid a record-setting heatwave in the eastern United States. 
Bryan Moran sprays his dog, Rocky, with water in Washington's Columbia Heights on Sunday. Eastern cities were forecast to approach or break record-high temperatures. 
Linda Gordon, right, finds relief from the extreme heat with an ice pack in Memphis, Tennessee, on Saturday, June 30. 
Residents crowd onto the beach at Coney Island in Brooklyn, New York, in the powerful heat on Saturday. 
Beachgoers lie in the sun at Coney Island on Saturday. 
A boy plays in the ocean at Coney Island on Saturday. 
Workers brave the high heat to repair a storm-damaged roof at the Park Tanglewood apartments in Riverdale, Maryland, on Saturday. 
Beads of sweat roll down Francisco Hernandez's face as he works to repave Hillsborough Street in Raleigh, North Carolina, on Friday, June 29. 
Children play in the water at Six Flags Over Georgia in Atlanta, where temperatures topped 100 degrees on Friday. - NEW: At least 16 states are under heat advisories or warnings on Monday
- NEW: National Weather Service: The Plains and the Atlantic Coast will feel "hot and hotter" for days
- Hundreds of thousands of people are left without power after weekend storms
- The storms, spurred in part by extreme heat, left at least 16 people dead
(CNN) -- Residents in the central and Eastern United States will sweat through another blistering day Monday as power outages from weekend storms continue to plague much of the country.
The intense early-summer weather has baked areas from Missouri to New York to Georgia with record-breaking heat and unleashed fierce storms that knocked out power to millions over the weekend. At least 16 people were killed from the series of storms.
While the pinnacle of heat has passed for many, so-called cooler temperatures Monday will still reach as high as 99 degrees for Louisville, Kentucky, and 96 degrees in Columbus, Ohio.
But triple-digit heat is expected to smother areas from Missouri to South Carolina on Monday, and at least 16 states are under heat advisories or warnings.
"Hot and hotter will continue to be the story from the Plains to the Atlantic Coast the next few days," the National Weather Service said Monday. "The widespread excessive heat warnings and heat advisories have certainly decreased in coverage, but temperatures will remain well above average across a large portion of the U.S."
Temps soar across the U.S. 
Heat wave, power outages hit mid-Atlantic 
U.S. heat wave affecting 100 million In addition, severe thunderstorms will be possible across the southern Mid-Atlantic region and north-central United States, the weather service said.
Federal agencies in the Washington area will remain open Monday, but nonemergency employees have the option to work remotely.
Cities and towns in the Southeast and Midwest have already endured temperatures of more than 100 degrees for days. For many, the misery is compounded by a lack of electricity.
Hundreds of thousands of people from Indiana through Maryland were dealing without power late Sunday after a massive storm late Friday and Saturday that was fueled, in part, by the extreme heat.
While down from a peak of about 4 million, the number of storm-related outages was still dangerously high given that people were trying to get by without working air conditioning or ice.
The APE Ohio utility company had about 425,000 customers out of power as of 10 p.m. Sunday. Widespread outages were reported farther east as well, including more than 310,000 Dominion customers in Virginia and more than 490,000 outages for BGE and Pepco customers in Maryland.
"It's the combination of heat and power outages that are hitting people," said Tamara McBride of the Ohio Emergency Management Agency. She predicted some may not get electricity until "well into the week."
Another bout of storms Sunday afternoon brought some relief to the heat but danger as well.
The National Weather Service reported that a man in Calico, North Carolina, was killed when a shed fell on him as he was trying to store his golf cart.
A few minutes later, in a nearby town, storm-related winds knocked over a tree that fell on a couple in a golf cart, killing them both.
More deaths tied to the weekend storms were reported from Ohio to New Jersey.
Virginia had the highest death toll, at seven, with the state Department of Emergency Management noting the deaths were spread across four counties.
And in New Jersey, 2-year-old and 7-year-old cousins died after a fallen tree crashed on the tent they were huddling inside in Parvin State Park, said Larry Ragonese, a spokesman for the state Department of Environmental Protection.
The stubborn, oppressive heat wave can cause serious health problems, with the effects of heat cumulative. The longer you experience it, the more likely you are to have conditions such as heat stroke and dehydration.
"Current indications are that this heat wave may continue for much of the upcoming work week," the National Weather Service's St. Louis bureau warned. "Do not wait until the heat wave has lasted for several days. Take action today to protect your health and continue to do so."
Between June 24 and Saturday 1,928 record-high temperatures were broken or tied nationwide. That number doesn't include new ones expected from Sunday that aren't in the National Climatic Data Center's official count.
But some tried to make the best of the roasting temperatures outside.
Holly Coons of Nashville decided to bake cookies on the dashboard of her car when it was 107 degrees outside.
"I actually burned my hand when I grabbed the cookie sheet out of the car," she said. But the cookies were done.
CNN's Rob Marciano, Jareen Imam, Josh Levs, Greg Botelho and Maggie Schneider contributed to this report.
