A dangerous, long-lasting heat wave that has brought triple-digit temperatures across much of the central and eastern United States was expected to continue Friday and into the weekend. Typical warm summer weather is not likely to return to much of the Northeast and Mid-Atlantic until Monday.
About 180 million people were under extreme heat warnings or heat advisories on Friday, and many had already faced several days of severe warnings to avoid going outdoors in the hottest parts of the day. Forecasters expect some of the highest temperatures around Philadelphia, which could reach 104. New York was about to hit 101 and Washington 103.
But sweat-inducing forecasts only tell part of the story.
On Friday, an Independence Day Semiquincentennial Parade in Philadelphia marking the 250th anniversary of the United States was canceled, with event organizers citing “extreme heat” in social media posts. In the nation's capital, organizers of the Great American State Fair postponed all daytime activities until 5 p.m. Eastern time, citing the heat in a social media post.
This followed conditions on Thursday when heat snarled train travel along the Northeast Corridor. Even the New England coast, a top vacation destination known as much for its relatively mild summers as its seafood, slowed under the weight of humidity as customers retreated indoors to enjoy air-conditioned comfort.
The heat also put pressure on power grids, contributing to scattered outages in New Jersey, New York and Ohio for tens of thousands of utility customers on Thursday, according to the tracking website PowerOutage.us.
More registrations are expected in the coming days. By Sunday, the National Weather Service expects more than 100 daily records to have been broken.
Key things to know about the heat wave
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On Thursday, Central Park hit 100 degrees for the first time since 2012, while Philadelphia hit 103, tying its record from 1,901.
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Conditions are worsening due to high humidity, leading to oppressive heat index readings. This index is a measure of how hot it actually feels outside.
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Temperatures dipping only into the 80s or 70s are allowing little relief and forecasters warned of heat-related illnesses. Heat is the leading cause of weather-related deaths in the United States. This is what it does to your body and here are some tips to keep you cool.
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While linking a single heat wave to climate change requires analysis, scientists have no doubt that heat waves around the world are getting hotter, more frequent and longer lasting.
The day-by-day forecast
Friday
“Dangerous, record-breaking heat” was expected to persist Friday across a widespread area between Illinois, Maine and Georgia, the Weather Service said. Temperatures were forecast to be similar to Thursday, with afternoon highs between 90 and 100 degrees. The heat index could reach 115 degrees.
By 11 a.m. Eastern Time, the heat index had already surpassed 100 degrees across the region, in some cases much higher. Washington was at 110 with an actual temperature of 97; Harrisburg, Pennsylvania, was at 105 with an actual temperature of 96; and in Richmond, Virginia, the index reached 104 with an actual temperature of 92.
Saturday
The 4th of July might bring some relief, but only a little. The most significant cooling is expected to occur in the Great Lakes and northern New England, with temperatures likely to dip into the low 80s.
Parts of the Northeast are likely to cool slightly, with Philadelphia, New York City and Boston likely to drop a few degrees from Friday's levels. But overall, everywhere from Massachusetts to the Carolinas is forecast to stay warm, with afternoon highs between 90 and 100 degrees once again.
New York City was projected to reach 99 on Independence Day and Philadelphia 100.
Brief showers and thunderstorms over the Mid-Atlantic and near Ohio could ease temperatures.
“The showers will be mostly scattered,” said Frank Pereira, a meteorologist with the Weather Prediction Center. “When they occur, they will provide temporary cooling, but once the sun comes out again, it will warm up again.”
The worst of Saturday's heat was expected in the area around Washington, with an expected high of 102, and south toward Raleigh, North Carolina, where the high could reach 105.
Sunday
Temperatures were expected to decline more broadly on Sunday, with a continued chance for showers and thunderstorms, particularly across much of the Mid-Atlantic.
Afternoon highs are likely to reach the 80s across much of the Northeast and New England, but warmth will remain in the southern Mid-Atlantic and Southeast.
Temperatures are forecast in the 90s for the area from Philadelphia to Washington, and triple-digit heat is expected in the Carolinas.
“The worst will be from Atlanta to North Carolina,” said Marc Chenard, a meteorologist with the Weather Prediction Center.
How to prevent heat-related illnesses
To stay safe during a heat wave, prevention is crucial. Drink water throughout the day and before you feel thirsty, and avoid going outdoors during the hottest parts of the day, usually from late morning to late afternoon.
It's important to recognize the warning signs of extreme heat exposure, and one of the earliest is heat edema, or swelling in the ankles, hands and feet, said Dr. Christopher Bazzoli, an emergency physician at the Cleveland Clinic. Early, mild symptoms can progress to full-blown heat stroke.
If you notice that kind of swelling, go to the coolest place possible, ideally somewhere with air conditioning. If you have to stay outside, find some shade. Elevating your feet can also help contain swelling.
Symptoms of heat exhaustion, a moderate form of heat illness, may include nausea, fainting or dizziness, muscle cramps, and a fast heartbeat. If you experience any of these symptoms, go to a cool place and rest and hydrate.
A more serious form of heat illness is heat stroke, which can be fatal. People who suffer heat stroke may develop a high body temperature (103 degrees or higher) and hot, red, dry or clammy skin. Symptoms also include headache, dizziness, nausea, and tachycardia.
When will the heat wave break out?
Not for a few days. A return to typical warm summer weather with widespread afternoon highs in the 80s from the Great Lakes to the northeast was expected by Monday.
New York City was projected to reach 81 and Philadelphia 83 on Monday.
But air conditioners may still operate in some areas, particularly in the Carolinas.
“It will get better for most people next week, but the Southeast will remain warm and humid, but nothing unprecedented,” Chenard said.
The report was contributed by Minho Kim, claire fahy, Jenna Russell, Dani Blum, Erin McCann and Nazaneen Ghaffar.
