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What's Behind This Week's Extreme Heat

heat wave weather map
A map of projected temperatures for the U.S. signals hot times are ahead. (Image credit: NOAA.)

Summer has begun with a bang, with scorching temperatures hitting huge parts of the United States on the first day of the sultry season.

Sizzling temperatures and wilting humidity hit the Mid-Atlantic and Northeast states today (June 20), prompting heat advisories in many major metropolitan areas. Extreme heat also hit the Midwest, where cities from Chicago to Milwaukee to Detroit saw afternoon highs in the 90s Fahrenheit (32 to 37 degrees Celsius), according to

The Great Plains and Southwest are likely to see sizzling temps in the coming days as well, according to the National Oceanic and Atmospheric Administration, which today produced a map that projects temperatures reaching as high as 108 F (42 C) in some places by the weekend.

Temperatures in the nation's capital soared to 98 F (36 C), one degree shy of its all-time heat record of 99, according to the Washington Post's Capital Weather Gang.

New York's Central Park saw a high of 94 F (34 C). "That is abnormally warm for this time of the year. It's been observed previously, but it doesn't happen often," said Joe Pollina, a meteorologist with the New York City office of the National Weather Service.

"The normal high for this time of year is 81 degrees," or 27 Celsius, Pollina told OurAmazingPlanet.

Several atmospheric conditions have conspired to send the mercury soaring, forecasters said.

A high-pressure system is parked off the East Coast, and since air travels clockwise around a high-pressure system, heat from the Southeast is being pulled toward the Northeast.

However, some of the heat seen in major cities in the eastern half of the country can't be chalked up to nature alone.

"All the asphalt and concrete tends to keep the heat in," Pollina said.

The peak of the heat will hit the East Coast tomorrow, Pollina said. "We're going to see highs around about 100 degrees in Central Park," he said. (That's 37.8 Celsius.)

But some relief is on the way: A cold front is moving in toward the eastern seaboard, and by Saturday, temperatures will drop — to around 85 F (29 C), which is slightly above normal, Pollina said.

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Andrea Mustain was a staff writer for Live Science from 2010 to 2012. She holds a B.S. degree from Northwestern University and an M.S. degree in broadcast journalism from Columbia University.