100 Million in U.S. Under Heat Alerts as First Summer Weekend Arrives (2024)

Millions nationwide face more hazardous heat as temperatures rise in the Mid-Atlantic states.

Over the next couple of days, some locations may see the highest temperatures they have experienced in years. In Washington, D.C., and other cities along the I-95 corridor, temperatures may exceed 100 degrees. If Washington hits 100, it will be the first time the nation’s capital has been that hot since Aug. 15, 2016.

The heat index, a measure of how conditions feel with humidity factored in, could reach 103 degrees or higher in Arizona, Texas, Louisiana, Florida, Kentucky and Ohio on Friday. Arizona, in particular, is in for brutally high temperatures: The heat index in the cities surrounding Phoenix is expected to reach 112 degrees, the highest in the country.

But forecasters say these Arizona cities are not threatened by the heat as much as some parts of the Midwest and Great Lakes regions, specifically Indiana and Ohio, as well as parts of Illinois, Pennsylvania and West Virginia, where people are less used to such extreme temperatures at this time of year.

Forecasters also warn that this could merely be the start of a summer of above-average temperatures across much of the country. Higher temperatures could return to the Northeast as early as next Wednesday.

Extremely hot summers have become increasingly common as climate change makes heat waves more frequent, longer and intense. One climate expert with the National Oceanic and Atmospheric Administration said that this year had already secured its place among the five warmest years on record — and that it might become the warmest ever.

The heat wave in New York will continue through the weekend.

Cooling centers, air-conditioned spaces open to all New Yorkers looking for a break from the heat, will be open through Sunday. (New York City maintains an online map of cooling centers that is updated in real time.)

Public beaches and state parks were again charging admission on Friday after Gov. Kathy Hochul announced that New Yorkers could visit certain sites for free on Wednesday and Thursday. Ms. Hochul said certain parks, including Bear Mountain, Jones Beach and Taconic, would add cooling features like sprays and misters through Friday.

Those looking for free places to escape the heat can find sprinklers, water fountains, beaches and shady parks on a map published online by the city’s parks department. The map will soon include the city’s 53 outdoor public pools, but not yet because they will not open until June 27.

The most severe heat is expected on Sunday, when the heat index, a measure of how hot it feels when humidity is accounted for, will reach 99 degrees in the city.

Nearly all libraries, which are among the city’s most reliable sources of air-conditioning for members of the public, are closed on Sundays because of budget cuts. But the city’s Emergency Management Department said that hundreds more centers would be open through Sunday on an emergency basis.

On Friday, the city began contacting homeless people to distribute supplies and encourage them to find air-conditioned shelter, a Department of Social Services spokesman said.

New Yorkers should also brace for possible power outages in the days ahead as millions of air-conditioners and fans run at once. The current heat wave is the first test for the city’s electric grid since last summer, and Con Ed, the utility that serves much of New York, expects some weak spots to fail, Patrick McHugh, Con Ed’s senior vice president of electric operations, said. Con Ed is prepared to make repairs as needed, Mr. McHugh said.

Strong winds downed power lines in Albany late Thursday, knocking out electricity for more than 10,000 National Grid customers, according to the utility. Around 7,000 New Jersey residents also lost power for several hours on Thursday. By Friday morning, power had been restored for most customers in both places.

Public schools in New York City were open and conducted classes as usual on Friday. The city began a $29 million effort in 2017 to install air-conditioning in every school, and now a “vast majority” of classrooms are air-conditioned, Daniel Weisberg, the first deputy schools chancellor, said at a news conference on Thursday.

Some schools north of the city, including those in Pelham, Yonkers and several districts in the Catskills and Hudson Valley, released students at noon on Friday after being unable to keep classrooms cool. Schools in those districts also had half-days on Thursday.

The Metropolitan Transportation Authority, which operates the city’s mass transit system, announced Friday that it would be on high alert through the weekend for potential heat-related service disruptions. The authority said extra personnel would be ready to fix outages at subway stations and to repair broken air-conditioning systems on subway cars and buses.

Trains operated by Amtrak and New Jersey Transit in and around New York were significantly delayed on Thursday and Friday, stranding some commuters in sweltering stations and train cars that lacked air-conditioning.

Reporting was contributed by Judson Jones, Tim Balk, Patrick McGeehan, Nate Schweber and Hilary Howard.

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Here’s what you need to know about the power grid during the latest heat wave.

Here’s what you need to know about power and the heat.

What is the status of the outages?

So far, there have been a limited number of power outages during the heat wave. And where they have occurred, storms were largely to blame.

In Southeast Michigan and the greater Pittsburgh area in Pennsylvania, powerful storms knocked out power for tens of thousands of customers. As of Friday afternoon, about 16,000 people in Michigan were still without electricity.

“We’ve just been hot and patient,” said Connie Wynn, whose power in Lathrup Village, Mich., has been out since Wednesday night.

An additional 48,000 customers lost power in Eastern New York on Thursday night because of storms and wind, but most of them had power again on Friday, according to National Grid, which provides service for the area.

On Thursday evening, about 6,800 New Jersey customers lost power, but most saw it restored as of Friday morning. The cause was still under investigation.

In New York City, there have been no major outages so far, according to Philip O’Brien, a spokesman for Con Edison, which serves the five boroughs and Westchester County.

As the heat wave slogged on for a fifth day, grid operators across the country were reporting that supply was keeping up with demand. That includes the operators that serve the Mid-Atlantic States, where temperatures are forecast to soar into the middle and upper 90s through the weekend, and the Midwest, where forecasters say swaths of Ohio and Indiana are especially at risk from the extreme heat.

What does this mean for the rest of the summer?

Experts said the performance of grids in this heat wave is reason for cautious optimism. The absence of blackouts is a promising sign that operators can handle high temperatures later in the summer, although much can change between now and then, they said.

Michael Webber, a professor and energy expert at the University of Texas at Austin, said the nation’s grids have had many factors working in their favor in this heat wave.

Spring maintenance means the infrastructure is fresh, and the heat wave has not hit the entire country, so grid operators can import power from other regions, he said. Operators have also added solar capacity, which performs well during heat waves, as the sun tends to be out. Plus, it is early in the summer, so the ground and infrastructure are not retaining as much heat from earlier periods as they will later in the year.

“I feel comfortable about where we are, but I don’t feel relaxed,” Mr. Webber said.

According to N.E.R.C., the grid has also been fortified by an increase in solar power and battery storage, which shores up supply. Grid operators are also doing more to expand programs that allow consumers to monitor and modify their energy consumption during times of peak demand, which can take pressure off the grid.

“We’re in better shape than last year, all things considered,” said Mr. Olson.

Still, N.E.R.C. has warned that large parts of the country are at risk of supply shortfalls during extreme conditions.

What can people do to prevent a blackout?

There are steps you can take to help prevent blackouts. Many are simple and inexpensive, such as setting your thermostat a few degrees higher and not cooling unused rooms. The load on the grid also varies throughout the day, so moving energy-intensive activities, such as running a washing machine or a dishwasher, to off-peak hours can help.

If you find yourself in a blackout, take action to stay cool. Blackouts during heat waves are not just a nuisance — they can be deadly, especially for those in populations that are vulnerable to extreme heat, such as older people.

Your priority during a blackout should be finding a way to stay cool, said Brian Calka of DTE Energy, which serves the region of Michigan that experienced outages. He recommended reaching out to friends, family or neighbors with power or seeking out a cooling center to escape the heat. If those steps are not possible, he encouraged covering up your windows to prevent your home from warming up and heading downstairs into a basem*nt, if possible.

Why was Maine sweltering?

The shift of this expansive band of heat toward the coast and farther north helped send temperatures soaring in New England, he said. It was part of a larger “high-pressure aloft” system, a type of phenomena that can produce heat domes.

Additionally, descending westerly winds off the mountain ranges in New England helped to further compress the heat into the lower elevations, which meant higher temperatures in many cities, Mr. Orrison added.

Now that same band of heat has moved further south and is sitting over New York City.

Although high-pressure systems closer to the surface mean fair weather, ones in the atmosphere (the so-called “aloft” systems) can mean days of sustained heat, with little cloud cover to disrupt the power of the sun.

As these high-pressure systems weaken, they can create space for low-pressure events to develop, which is why thunderstorms threatened the area yesterday.

And then there is climate change. The continued burning of greenhouse gases means that the temperature of the atmosphere is increasing almost everywhere, said Jason Smerdon, a professor at the Columbia Climate School.

Though the underlying causes of the most recent heat wave in the Northeast are yet to be determined, he said, the combination of high temperatures and humid conditions created a “double whammy” effect, since a warmer atmosphere holds more moisture.

“So the ‘feels-like’ temperature from combined heat and humidity made the event particularly severe,” he said.

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A ride in a chemical-sniffing van shows how heat amps up pollution.

“If you want a chemical reaction to go faster, you add heat,” said Peter DeCarlo, an atmospheric air pollution researcher at Johns Hopkins University who’s leading an effort to use the vans to measure emissions along Louisiana’s petrochemicals corridor. “On hotter days, it’s the same idea,” he said.

Air pollution surges when temperatures rise, adding to the harms wrought by global warming. It’s one reason cities and counties across the Eastern United States hit by a heat wave this week have been issuing air pollution alerts.

The past three days, New York City has warned that ozone in the city is at levels “unhealthy for sensitive groups.” Detroit and Chicago have also issued air quality alerts this week. Drivers in Ohio, Michigan, Kentucky and Indiana have been urged to avoid refueling before 8 p.m., and to car pool or refrain from driving as much as possible, to cut down on fumes.

The bad air has to do with atmospheric chemistry, Prof. DeCarlo said, while his van navigated the South Bronx, East Harlem and Midtown with two New York Times journalists along for the ride. Pollution from burning fossil fuels reacts with heat and sunlight, forming ground-level ozone. Higher temperatures turbocharge that process.

Formaldehyde emissions, which can come from sources as diverse as wildfires and household products, also rise with higher temperatures. “The same chemistry that generates high levels of ozone also produces additional hazardous air pollutants, such as formaldehyde,” Prof. DeCarlo said.

Local hot spots can sometimes be seen. For instance, on some blocks in Manhattan, formaldehyde levels were double the surrounding areas, possibly from particularly dirty combustion caused by faulty equipment nearby.

The heat-pollution nexus is a growing concern worldwide. Health harms from extreme heat aren’t the only outcome of record-breaking temperatures. Air pollution also spikes when the temperatures rise, the World Meteorological Organization said in a report last year.

“Climate change and air quality cannot be treated separately,” Petteri Taalas, the weather organization’s secretary-general, said at the time. “They go hand in hand and must be tackled together to break this vicious cycle.”

Breathing elevated levels of formaldehyde and ozone has been linked to problems like respiratory irritation and inflammation, reduced lung function, and difficulties preventing and controlling asthma attacks. Exposure is particularly concerning in people with lung diseases like asthma or chronic bronchitis, said Keeve Nachman, an environmental-health and risk-assessment researcher at Johns Hopkins and a co-lead on the mobile monitoring effort.

By coincidence this week, as New York was getting struck by the heat wave, the research team had its pollution-sniffing vans in the city to demonstrate their technology.

Prof. Nachman said that while formaldehyde was carcinogenic to humans, cancers would be expected primarily from longer-term exposures, not from temporary increases.

It’s also important to recognize that chemical exposures don’t happen one at a time, and that we’re constantly exposed to groups of chemicals that may act together to harm our health, he said. “Hot days can create situations where people are breathing many harmful chemicals at the same time,” Prof. Nachman said. “Formaldehyde and ozone are perfect examples.”

One of the vans is set to return to Louisiana later this year to measure for as many as 45 pollutants from its petrochemicals industry, part of a project funded by Bloomberg Philanthropies’ Beyond Petrochemicals Campaign. In an initial peer-reviewed study published this month, the researchers found far higher emissions of ethylene oxide, a carcinogenic gas used in plastic production, than previously known.

Researchers piloting the van, a high-tech lab-on-wheels built by the environmental measurement tech company Aerodyne, can see pollution levels in real time, and even follow plumes to try to determine their source. “It’s a bit like a video game,” Prof. DeCarlo said. “And we’re able to measure everything all at once.”

Blacki Migliozzi contributed reporting.

How to stay cool indoors during the heat wave.

What’s the ideal temperature for your home?

While you should do what feels most comfortable for you, Carrier, an air-conditioner manufacturer, suggests on its website that 72 degrees is the generally accepted “comfortable indoor temperature for many people.” It continues, “It strikes a good balance between comfort and energy efficiency, making it a popular choice for residential settings.”

If you’re away from your home, set your thermostat for higher than usual to save energy and to prevent your AC unit from potentially busting. At night, because heat can disrupt sleep, 60 to 67 degrees is recommended by the Cleveland Clinic.

How do you keep your furry friends safe?

It depends on the animal, and its size and type, but pets are generally less tolerant of higher temperatures than humans.

Dogs, the most common pet in the country, tend to overheat when the temperature is between 81 and 85 degrees, according to the American Kennel Club. “An ideal temperature doesn’t exist for all dogs, since their normal body temperature will vary according to size,” the organization states on its website. It also suggests installing a temperature alarm that can notify your phone if your AC fails and you’re not at home to notice.

How do you maintain your AC?

If your AC is broken, it might be too late to find a repairman to fix it in time for the heat wave, but going forward, experts recommend servicing your AC unit once a year. A technician will typically check for and diagnose issues with the system, clean it and change out the filter.

Depending on your unit, you may be able to change your filter yourself. Carrier suggests inspecting your filter every two to three months, and certain factors might affect how often you’ll need to change it. (For example, if you have a pet, you may need to replace the filter more frequently because of its shedding.) You can look for an online guide on how to change the filter — whether it is for a window unit, floor-mounted or other. Just make sure to turn your system off first.

What can you do if you don’t have an AC?

You can close your blinds or cover your windows to minimize your exposure to direct sunlight. Stick-on solar film, which can be bought online or at home-improvement stores, is also an option. This can deflect infrared heat that would otherwise come in through your windows.

What are some things to avoid indoors?

Steer clear of using appliances that generate heat, such as an oven, clothes dryer, iron or blow dryer. New York Times Cooking has a list of “No-Cook Recipes for a Heat Wave” so you can prep a meal without turning on your stove top.

Try to avoid dark fabrics for curtains, upholstery or clothing, as they can absorb heat more easily. You can also turn off lights — having too many on close together can heat the surrounding air.

Avoid thick covers and blankets. Percale sheets tend to be more breathable, and Wirecutter has a guide for bedsheets for hot sleepers.

Can I report my landlord if my apartment is unreasonably hot?

While some cities, like Dallas, have air-conditioning requirements for rental apartments, New York City does not. (Landlords in New York are legally obligated to provide heat and hot water.) But if you live in an apartment that had an AC when you moved in, landlords are responsible for maintaining it and replacing it if it’s broken.

If they refuse to fix it or are unresponsive, you have options. Ronda Kaysen, a real estate reporter and former “Ask Real Estate” columnist, suggests paying to replace the AC unit yourself if you can then negotiate your rent, asking for the same amount for the upcoming year. You could also take your landlord to court, but that could be more time-consuming and expensive than paying to fix it yourself.

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A short guide to understanding heat domes.

A heat dome is a high pressure system way up in the atmosphere that helps create and encase heat, kind of like a lid on a pot that holds in steam.

Heat domes “on the order of 1,000 miles across” can form under high pressure weather systems, said Hosmay Lopez, an oceanographer and expert on extreme heat and climate change with the National Oceanic and Atmospheric Administration. They become anchored in place, building up heat, sometimes for weeks at a time.

The term “heat wave” describes a rise in temperature in the weather pattern, and the term “heat dome” refers to a high pressure system that traps heat. The terms are often used interchangeably.

How do heat domes form?

When a high pressure system moves into an area, it pushes warm air toward the ground. With the sinking air acting like a cap, the warm air can’t easily escape, and it continues to heat up the more it is compressed.

“You can actually repeat this process on a small scale,” said Greg Carbin, forecast operations chief at the National Weather Service’s Weather Prediction Center. “When you’re inflating a flat tire, as the air goes in and the pressure builds, the molecules move faster, they are closer together, and they heat up.”

This high atmospheric pressure is linked to the configuration of the jet streams, bands of speedy winds that form high in the atmosphere in areas where cold air and hot air meet. The jet streams tend to be narrow, wavy corridors of air that move west to east and migrate north to south. Sometimes jet streams can expand, becoming slower, or even stagnant, and heavier.

Can heat domes happen anywhere?

Yes, they can, but areas that are farther from water, have flatter topography and are south of where jet streams migrate in the summer are more prone to oppressive heat domes. In the United States, that area is the Central Plains.

The heat domes that have covered the Pacific Northwest in recent years still baffle meteorologists, Mr. Carbin said, because the mountainous topography of the region is the opposite of what is usually conducive to heat domes.

Heat domes are associated with climate change. In the 1970s, there was one heat wave for every cold wave. As climate change accelerates, “that ratio is more than two to one, and for some places, it’s three to one,” Dr. Lopez said.

Are heat domes dangerous?

Yes. Heat stress is the most common cause of weather-related deaths, according to the World Health Organization. Because heat domes are associated with stagnating air, they can also lead to reduced air quality, dryness and a greater chance of fire. “Those stains are very detrimental for human health, especially for the elderly and people with preconditions like cardiopulmonary illnesses,” Dr. Lopez said.

Read about staying safe in a heat wave here.