Heat wave strains power grid; millions warned of danger: Updates

WASHINGTON – A deadly, record-setting heat wave was continuing to blast most of the eastern U.S. on Tuesday, June 24, forecasters said, with temperatures soaring to near 100 degrees for tens of millions of people.

A woman in the St. Louis area died in her home due to the dangerous heat after having no water or air conditioning for at least three days, KDSK-TV reported.

And in New York City on June 24, the temperature at JFK Airport rocketed up to 102 degrees, which is the hottest reading ever recorded there in June, the National Weather Service said.

This comes a day after temperatures topped 100 degrees in both Newark, New Jersey, and downtown Baltimore and thousands of customers lost power due to the excessive heat.

Extreme heat warnings and heat advisories remained in place all the way from St. Louis to Boston on June 24, the said. Other cities enduring these alerts include Chicago, Detroit, Cincinnati, Pittsburgh, Philadelphia, Washington D.C. and New York City.

Manhattan is shrouded in an afternoon haze seen from Staten Island on June 23, 2025 in New York City. Temperatures in New York City reached into the high 90s as the first heat wave of the year moved across parts of the Midwest and East Coast.

About 33 million people, almost 10% of the country, will feel blistering 100-degree heat on June 24, meteorologist Ryan Maue told the Associated Press. Maue added on X that every state along the Atlantic coast from Florida to Maine could hit 100 degrees on June 24.

Heat wave skyrockets electricity demand

Electricity demand skyrocketed June 23 to the highest level in more than a decade, prompting the largest U.S. power grid operator to issue an emergency alert, as Americans crank up their air conditioners and fans to beat the summer heat.

PJM Interconnection, which provides power to about one-in-five Americans, said demand reached about 161,000 megawatts June 23, the highest level recorded since 2011. They expect a similar level of demand on June 24. 

Daniel Lockwood, a spokesperson for the PJM said it has “sufficient reserves to meet customer demand” through the heat wave.

On a typical day, one megawatt powers about 800 homes, but that number dips on hot summer days. The heat creates a double whammy for the electrical grid, according to the Department of Energy’s Pacific Northwest National Laboratory.  

Demand for electricity soars as people blast their air conditioning, while the heat decreases the ability of systems like natural gas turbines and solar panels to generate and transmit electricity, according to a 2024 blog post from the agency.  

– Karissa Waddick

Could heat impact NYC's primary election?

On Tuesday, June 24, as residents of the five boroughs of New York City headed to the polls to cast their ballots in what promises to be a unique primary election, heat radiated off the concrete.

Central Park soared to a record 98 degrees by early afternoon, and officials sent out a heat advisory, urging residents to stay hydrated and cool, whether on their way to work or to the polling station.

Whether the heat wave will affect voter turnout remains to be seen, but candidates have already begun to express concern over the Board of Elections' ability to handle any potential power outages at polling stations should they arise.

– Anna Kaufman

'Dangerous heat'

"Dangerous heat will maximize across much of the Northeast and mid-Atlantic early this week," said AccuWeather meteorologist Jacob Hinson in an online forecast June 23.

In major cities such as Washington, D.C., Baltimore, Philadelphia and New York, the temperature was forecast to approach 100 degrees through at least June 24, which would mark the first time in many decades that triple-digit heat has been experienced in June, AccuWeather said.

Even parts of eastern and northern New England, including Boston and Portland, Maine, which are sometimes excluded from extreme heat, will come within a few degrees of 100 when the heat peaks on June 24, AccuWeather said.

Meanwhile, overnight lows are forecast to drop only into the 70s, with urban centers along the East Coast struggling to drop below 80 degrees at night, the National Weather Service said.

In fact, the temperature failed to drop below 80 degrees in New York City, Newark and Philadelphia on the morning of June 24, the weather service reported.

Power outages reported

Thousands of power outages were reported in Pennsylvania, New Jersey and New York on June 24. According to Poweroutage.us, over 12,000 customers were without electricity in Pennsylvania, where thousands could be without power for days after a fire damaged an electrical substation in northern Adams County, according to Met-Ed estimates.

As viewed early on June 24, estimates for the restoration of power for several thousand in the area was listed as 11 p.m. on Thursday, June 26.

More than 9,000 customers were powerless in New York, and over 4,000 people in New Jersey were without power in the midst of the extreme heat wave, according to online data. That's down from over 30,000 in New Jersey on June 23.

– Kyle Morel and John Connolly, NorthJersey.com; Harrison Jones, Hanover Evening Sun 

A record-smashing heat wave

The heat wave has already "smashed records not just for a particular calendar day, but also anytime in June," noted Weather.com meteorologist Jonathan Erdman. "In a few locations, it's even tied or set new all-time records."

Plattsburgh, New York, tied its all-time record high of 101 degrees June 24, the National Weather Service said. This tied the mark set twice before, on August 1 and 2, 1975, and again on August 5, 1955.

On the shores of Lake Champlain, the city reached 100 degrees for only the fourth time in its almost 80-year period of record, Erdman said.

Several all-time records for warm overnight lows were also set or tied in the Midwest over the past several days, including in Green Bay, Wisconsin (79 degrees) and Lansing, Michigan (78 degrees).

A June record was tied June 23 in North Hartland, Vermont: This small town near the New Hampshire border soared to 101 degrees June 23, tying Vermont's June record with St. Johnsbury on June 4-5, 1919, according to weather records expert Maxmiliano Herrera and weather historian Christopher Burt.

Amazingly, this Vermont town was hotter than both Tucson and Yuma, Arizona, Monday (each reached 99 degrees), Erdman said.

Also Monday June 23, Baltimore's Inner Harbor soared to 104 degrees, just 2 degrees shy of the nation's hottest temperature (106 at Death Valley), he said.

How to stay safe in the heat

• Use sunblock or sunscreen: And reapply it regularly (every two hours is a good baseline.)
• Dress for the heat: Pick loose-fitting, light-colored and lightweight clothes, the National Weather Service recommends.
• Don't leave kids or pets in the car: The temperature quickly becomes deadly − even if it's not that hot out.
• Check the weather: Your favorite weather app should have a wealth of information about UV index (for sunblock purposes), heat warnings and the feels-like temperature. Heat.gov has additional information about the forecast and heat risk.
• Bring water: You'll need multiple bottles of water per person if you're spending extended time in the sun. (How many bottles? .)
• Seek shade and air conditioning: Minimize your risk by staying cool and avoiding direct sun when you can.
• Know your risks: Heat is dangerous for everyone, but some people are more vulnerable than others. Being a child, over 65 or pregnant puts you at greater risk, the Centers for Disease Control and Prevention says.

— Joel Shannon

Tourists grapple with heat in nation's capital

Evidence of the near 100-degree temperatures in Washington D.C. was evident Monday afternoon on the National Mall as tourists, lined up at street vendors selling water and ice cream, took refuge in the shade of trees and camped out in museums to beat the heat.

At a small water fountain and splash pad near the Washington Monument – which was closed due to the heat – Harikrishna Gopalan and his family washed themselves off after a short, humid walk from the Smithsonian’s National Air and Space Museum.

Gopalan, 42, who is from Dubai, said he was surprised by the sweltering heat in Washington but said it’s comparable to a “winter afternoon” in his home country.

He added, however, that Dubai seems much more prepared to deal with the heat. For example he said businesses and museums shift their hours to stay open until nightfall and bus stops are equipped with air conditioners.

“I wish the museum didn't close at 5:30,” he said, tugging on the neck of his sweat-drenched shirt. Nearby, his daughter took off her shoes and splashed in the water.

“I knew it was going to be hot – but not like this,” Gopalan added.

To avoid the worst of the heat, Samantha Larsen rearranged the itinerary of her family’s trip to Washington from Louisiana.

Instead of walking along the National Mall on Tuesday, they toured the monuments around 8 p.m. on Monday, though the heat index was still near 100 degrees when they reached their first stop.

Using her hand to shield her eyes from the setting sun, Larsen said she was glad for the schedule change so she could spend Tuesday inside the nearby museums.

“We are definitely staying inside all day tomorrow,” she said, squinting as she looked up at the closed Washington Monument.

The climate change connection to heat

Of all the weather impacts linked to human-caused climate change, extreme heat poses the biggest threat to human life – more dangerous than even floods or hurricanes.

Scientists have warned that such extremes are fast becoming the new normal – while also upending assumptions about which regions might be spared the worst of climate change.

"A lot of people ask the question, 'where is it safe to be?' And the answer is probably – no place," said Howard Frumkin, an expert in environmental and occupational health sciences at the University of Washington. "We did not think the upper Midwest was going to be vulnerable to heat extremes."

The heat was also being felt in Britain, while the Arctic state of Alaska registered its first ever heat advisory last week. Last month, China saw its temperatures soar.

Humidity is adding to the misery

This will particularly be the case in the mid-Mississippi and Ohio Valleys, but also into the Great Lakes and mid-Atlantic and Northeast. "That means the heat index, or feels-like temperature, will be in the triple digits on one or more days for some cities in the Midwest and Northeast," he said.

How long will the heat last?

The brutal late-June heat wave is causing sweltering folks to wonder when it will finally end.

It all depends on location, forecasters said, with some seeing relief as early as Tuesday, June 24, while others may not see any cooling temperatures until later in the week.

In some spots, the extreme heat is expected to last through much of this week, the weather service said June 23. The most significant heat impacts are anticipated across the Mid-Atlantic through Thursday, June 26 and the eastern Ohio Valley into Friday, June 27, "leading to several consecutive days of oppressive heat."

The longest duration of well above-average temperatures will be centered over the eastern Ohio Valley into Friday June 27, the weather service said.

Folks in the upper Midwest and northern New England will see some relief Tuesday, June 24, and Wednesday, June 25, while the Northeast will have to wait until at least Thursday June 26.

According to AccuWeather, cooling thunderstorms will also offer brief reprieves from the heat, but not the humidity, in some areas this week. "In addition to gusty storms on the periphery of the heat dome from the Plains to New England, pop-up thunderstorms can bubble up and fizzle out in a random nature, especially across the South," said AccuWeather meteorologist Bill Deger.

Heat index forecast map

Watch for heat-related illnesses

This heat level can be dangerous to anyone without effective cooling and/or adequate hydration, especially those engaging in lengthy outdoor activities, the weather service warned. Heat-related illnesses increase significantly during extreme heat. "Take action when you see symptoms of heat exhaustion and heat stroke," the weather service said.

Staying hydrated and taking breaks away from the sun are helpful practices during the ongoing heat wave, Dr. Evan Kuhl, an emergency care physician at the University of Louisville's Jewish Hospital, said during a news conference June 23.

Certain groups are at a higher risk for heat-related illnesses, including the elderly and people with pre-existing health conditions, Kuhl said. With this in mind, it is a good idea to check on neighbors as the warm weather continues.

Contributing: Leo Bertucci, Louisville Courier Journal; Reuters