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What's Behind the Blazing U.S. Heat Wave?

A relentless heat wave has been burning its way across the country this week, setting record high temperatures in city after city. The force behind the blazing heat? A mass of high-pressure air.

Earlier in the week, the heat wave terrorized much of the Midwest and South, boosting temperatures in Houston to an all-time June record of 105 degrees Fahrenheit (40.5 degrees Celsius) on Sunday (June 5).

Dozens of other heat records have been broken this week, causing heat-related health issues in many cities, such as New York and Philadelphia.

The atmospheric phenomenon fueling the hot weather is called a high-pressure ridge. This ridge is essentially a long area of high atmospheric pressure. These often contain dry air, and block clouds and rain.

"A lot of warm, dry air in the ridge makes it very easy to heat the air at the surface," said Jim Moser, a meteorologist with the National Weather Service (NWS) in Nashville, Tenn., a city that also set a temperature record on Sunday of 97 degrees F (36 degrees C).

These ridges are typical during the summer, but "it just happened to happen a little bit early this time," said John Lake, a meteorologist with the NWS in Fort Worth, Texas. Houston's record-setting day was the earliest 100-degree day in the state's history.

Midweek, the heat wave moved over the eastern states, setting records in Newark, N.J. (97 F; 36 C), Washington, D.C. (99 F; 37 C), and Philadelphia (97 F; 36 C). More records could be set today (June 9) before the heat wave breaks in the East. Cities such as Minneapolis, which set a high of 103 F on Tuesday (June 7) are already clear of the punishing heat after the ridge moved through.

Other cities that set daily records this week included:

  • Waco, Texas 101 degrees F (38 degrees C)
  • Colorado Springs, Colo. - 92 degrees F (33 degrees C)
  • Nashville, Tenn. 97 degrees F (36 degrees C)
  • Baton Rouge, La. 99 degrees F (37 degrees C)
  • Hattiesburg, Miss. - 102 degrees F (39 degrees C)
  • Ft. Smith, Ark. - 98 degrees F (36.6 degrees C)