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Those Summer Nights Are No Longer a Refuge From Extreme Heat

  • High nighttime temperatures can cause health problems
  • Records could be set for overnight lows in Texas, U.S. South

It’s going to be so hot in Texas and across the southern Great Plains that when the sun goes down, the temperature won’t.

Overnight lows will remain above 80 degrees Fahrenheit (27 Celsius) in Houston during the next week and will hover in the high 70s in Dallas and Tulsa, Oklahoma, the National Weather Service said. This extends recent trends: Across the U.S. in the past week, there were 230 overnight heat records and only 38 daytime highs, according to the National Centers for Environmental Information in Asheville, North Carolina.

“It is not good,” said Jerry Meehl, a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado. Heatwaves and high overnight temperatures are a bellwether for how hot the Earth is getting: As average temperatures rise, so do those overnight lows.

The nighttime heat is boosting demand for electricity at a time when power traders are typically ignoring the market amid a drop-off in use. Consumption across Texas was projected by the state grid operator to peak at 66,730 megawatts on Wednesday, nearly 2,000 megawatts above the forecast for a day earlier.

The late heat is “bullish for overnight demand when demand would typically fall off," said Kyle Cooper, director of research for IAF Advisors in Houston. "That goes back to the idea that you still have to keep the lights on and have units available for generation at night when previously you didn’t."

Nighttime heat can also bring grim results. Cooler evenings offer a chance for people to recover after a hot day in the sun. When temperatures stay high for long periods, those without access to shelters or air conditioners can face deadly consequences.

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“Nighttime temperatures are definitely a challenge, especially for people who don’t have a working A.C. unit in their homes,” said Zachary Thompson, director of Dallas County Health and Human Services. “You are still talking about 80 degrees and above; at night your body cannot cool off.”

In Texas and the Southern Plains, there may be no daily heat records this week, though overnight temperatures may reach new highs, according to the National Weather Service. The high in Houston was 97 degrees on Tuesday, well short of the record 102 in 2009. The low was 83 degrees, 8 above normal.

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