NEW YORK – Summer is here, and it’s gearing up to be a hot one, as extreme heat becomes a major concern through next week. 

A sprawling high-pressure system, also known as a heat dome, is settling over the U.S. during the first full week of summer, ready to bake more than 30 states in extreme temps.

Heat alerts are in place all across the Plains through the weekend. 

Beginning Friday, areas such as Denver will feel the heat, with temperatures topping 100 degrees, according to the FOX Forecast Center. 

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By Sunday, more than 200 million Americans will see temperatures at or above 90 degrees. High humidity makes for warm nights, offering very little relief from the extreme daytime temps. 

The heat wave will peak in intensity and impact early next week as the strong ridge of high pressure settles over the East. Temperatures in the Northeast are forecast to soar to levels rarely seen during the month of June.

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New York City and Philadelphia will flirt with 100 degrees by Monday, a rare occurrence in June. 

Daily high temperature records that date back to the 19th century are expected to be broken in New York City, Pittsburgh and Trenton, New Jersey. 

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The National Weather Service’s HeatRisk map showed extreme temperatures across several states on Monday and Tuesday. 

On the HeatRisk map, the most dangerous heat levels are marked “extreme.” According to the NWS, this level of rare and/or long-duration extreme heat with little to no overnight relief affects anyone without effective cooling and/or adequate hydration. 

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“You don’t see the extreme color painted on a map like this that often,” said FOX Weather Meteorologist Stephen Morgan. “So to see almost entire states under that extreme risk, it’s the real deal.” 

The heat should start to ease for much of the country Wednesday as temperatures return to near-normal levels for June.