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Holy Heat Wave! Thermometer-Popping Temps Continue in U.S.
This image shows the NOAA North America Model temperature at about 6 feet for July 12.
Credit: NOAA.

If you've got it made in the shade this week, consider yourself lucky. A major heat wave is sweeping across much of the country.

A look at the U.S. weather map shows a lot of red and pink. Temperatures are expected to soar past 100 degrees Fahrenheit (38 degrees Celsius) in many cities, and 24 states are under heat advisories.

Across the country this month, 669 heat records have been either tied or broken, according to the National Climatic Data Center. Oklahoma City has had 100-degree F temperatures every day this month.

"We're definitely on the road to a very hot and dry summer," said Daryl Williams of the National Weather Service in Norman, Okla. "The pattern doesn't look to be changing anytime soon."

Stubborn ridge

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

The high-pressure pattern has settled over the middle of the country. Cooler air hasn't been able to break through.

The severe drought across 14 states is not helping. Cooling summer rain has been scarce where it's needed most.

"Many times when we have a wet spring, we may not get 100 degree temps until September," Williams told OurAmazingPlanet. "We got into our hot pattern early."

A similar ridge settled over Middle America earlier this year, causing an early outbreak of 100 F temperatures. During that heat wave, Houston set an all-time June record of 105 F (40.5 degrees Celsius).

Record wave

Many cities along the Interstate 35 corridor, from Kansas to Texas, have already seen a normal year's worth of 100 F days, the Weather Channel reported.

Oklahoma City has already seen 21 100-degree days this year. That is 11 more 100-degree days than its annual average. On June 9, the thermometer hit 110 F (43 C), the city's highest temperature in 15 years, Williams said. [Related: What's the Highest Temperature Ever Recorded in the U.S.? ]

Wichita, Kan., has seen 18 100-degree days. Its annual average is 14 days. Austin, Texas, has already doubled its annual average of 100-degree days. Dallas is closing in on its average.

All this, and the August dog days of summer are still weeks away.