Weather Updates

Heat ‘dome’ puts much of U.S. in pressure cooker

Seeking relief from muggy weather hot temperatures two-and-a-half-year old Gordy Bartsh Fargo runs through spray water MadisPool Monday July 18

Seeking relief from the muggy weather and hot temperatures, two-and-a-half-year old Gordy Bartsh, of Fargo, runs through a spray of water at the Madison Pool Monday, July 18, 2011, in north Fargo, N.D. (AP Photo/The Forum, Dave Wallis)

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Updated: July 20, 2011 1:07PM

For millions of people enduring this week’s extreme heat and humidity in Chicago and throughout much of the United States, it feels like they’re living in a pressure cooker. And in a sense, they are.

Meteorologists say much of the country is trapped under a heat “dome” caused by a huge area of high pressure that’s compressing hot, moist air beneath it. The dome is producing temperatures in the mid-90s to low 100s and heat-index levels well above 100 degrees from the northern Plains to Texas and from Nebraska to the Ohio Valley.

The dome pushes the jet stream and its drier, cooler air farther north — it’s now well into Canada, said Eli Jacks, a meteorologist with the National Weather Service.

And hot, humid air from the Gulf of Mexico circulates around the dome and travels farther inland than normal.

Combined with generally clear skies and the sun’s higher summertime angle, “it gets really hot,” Jacks said.

That also explains why temperatures around Chicago and even as far north as North Dakota aren’t much different this week from what they are in Houston. The big difference, of course: People in Houston are more accustomed to it. AP

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