Unrelenting Heat Stifles Millions of Americans for 3rd Consecutive Day

From the Midwest to the northern tip of Maine, millions of Americans sweltered under a springtime heat wave on Wednesday that stifled the Eastern portion of the United States for a third consecutive day.

As the heat wave moved east, the Northeast felt the brunt of the conditions, stemming from a high-pressure system called a heat dome that scorched the Great Lakes region earlier this week.

Conditions in a swath of central Maine were particularly brutal, largely because the area was farther from ocean winds, according to Jay Engle, a forecaster at the National Weather Service. The heat index — a measure that includes temperature and humidity to showcase how hot it actually feels — topped 100 degrees in some areas, and temperatures reached as high as 95 degrees in cities like Bangor, Houlton and Millinocket, according to the National Weather Service. In Caribou, in the northeastern tip of the state, it was 96 degrees, tying the highest temperature ever recorded there.

More than 78 million people were under heat warnings, watches and advisories on Wednesday, according to the National Weather Service. Heat waves are not uncommon in mid-June, but the Weather Service warned that this one could last longer than some places have experienced in decades. Heat waves are also hotter, more frequent and longer lasting now because of global warming.

But forecasters provided a glimmer of relief: Meteorologists at the Weather Prediction Center said in a post on its website that “conditions should improve over New England” this weekend.

Still, in many areas, Wednesday felt more like the height of summer than the last full day of spring. Cities and states helped residents deal with the stifling temperatures by opening more cooling centers, moving some Juneteenth celebrations indoors and pushing up opening hours of pools and beaches.

In New York, Gov. Kathy Hochul announced free admissions to state parks. Around Maine, officials added more cooling centers by turning libraries, town halls, civic centers, Y.M.C.A.s and fire departments into places of reprieve. And Amtrak warned of possible delays along its service through the east coast of New Hampshire, Massachusetts and Maine because of heat-related speed restrictions.

Thousands in Pittsburgh and other parts of western Pennsylvania dealt with the double challenge of the heat and power outages.

Earlier this week, a series of damaging wind and rain storms knocked out power for as many as 85,000 customers at one point, and some 3,000 people were still without power. Utility crews from across Pennsylvania and nearby Ohio and West Virginia have been scrambling to restore electrical lines. The heat index in western Pennsylvania has been in the 90s, and could reach over 100 degrees this week.

But the heat didn’t deter some Americans from spending the day outside. In Chicago, about 300 cyclists rode through downtown to celebrate the Juneteenth holiday. As midday temperatures approached 90 degrees, a group of about 20 tourists went on a walking tour of the city’s financial district.

In New Hampshire, crowds flocked to Wallis Sands State Beach. According to Ryan Dennehy, who works at the entry gate, more people seemed to come on Wednesday than on the Fourth of July.

For some, though, spending much of the day in the heat wasn’t a choice.

William Daugherty, a 60-year-old safety manager who was working with his crew to install an underground pipeline in Middletown, Ohio, placed a cold towel on his head and later wrapped it around his neck to cool down. He also set up a shade tent with a blower and a bucket of ice for other workers to get a respite from the heat.

And for the homeless like Chris Adkins, 48, who lives in a tent by the Great Miami River in Ohio, the heat is especially tough. Mr. Adkins went to New Life Mission, a church that was providing meals and a cool space for those in need, for a break from the stifling weather.

“For me, the heat is worse than cold,” Mr. Adkins said. “You can always build a fire when it’s cold.”

Temperatures might improve over the weekend in New England, the Weather Service said, but the Ohio Valley and the Mid-Atlantic is forecast to continue to bake. Some cities, like Pittsburgh, had excessive heat warnings and advisories extended into Saturday night.

For New York City, Sunday might be the hottest day in this heat wave, until a cold front breaks it on Monday, Mr. Engle said.

“We might not be in a heat advisory criteria, but it’s going to be very hot, very warm and humid,” Mr. Engle said.

John Keefe, Robert Chiarito, Michael Corkery, Sydney Cromwell, Rhianwen Watkins and Kevin Williams contributed reporting.