Heat Wave Blankets Much Of The U.S. This Week

Enlarge this image toggle caption Paul Sancya/AP Paul Sancya/AP

Dangerously hot weather is hitting most of the U.S. this week, the National Weather Service says. Temperatures are expected to soar across the Central and Eastern United States. The heat wave is covering the Central Plains from Eastern Colorado into Kansas, and extending up to the Great Lakes. By Saturday it will blanket much of the East Coast from Virginia up through New York City, where temperatures are expected to reach or be close to 100 degrees.

Gentry Trotter is a founder of Cool Down St. Louis, a nonprofit group in St. Louis, Mo., which helps low-income families with their utility bills and donates air conditioners to people who are elderly or have physical disabilities.

Trotter tells NPR, "It's been very hectic. It has been blazing hot. What we're worried about now is making sure that people, especially seniors and the physically disabled, stay hydrated. That they have a place to be cool at."

Enlarge this image toggle caption Drew Angerer/Getty Images Drew Angerer/Getty Images

Meteorologists say a high-pressure heat dome will trap summer heat across much of the country, smashing records. Richard Bann, with the National Weather Service Weather Prediction Center, tells NPR the dome will deflect weather patterns around its periphery. "Global disturbances won't penetrate [the heat dome]," Bann says. "They might just move around this big dome of heat. We get maybe a few showers and maybe a few thunderstorms at the core of this, but it's basically a part of the atmosphere where it's warmest at the center of this dome."

The heat wave is caused by a jet stream moving north, which allows tropical hot air from the Gulf of Mexico and the tropical Atlantic to stream northward over the eastern half of North America. The intensity and length of this heat wave is unusual. It is expected to last for several days.

Jennifer Francis, a senior scientist at the Woods Hole Research Center, told NPR the frequency of heat waves is increasing, and their persistence is likely linked to climate change.

"We're seeing heat waves ride on a background temperature that is just getting warmer. So if you've got a situation where temperatures are ten degrees warmer than normal, normal itself is actually getting warmer. So a heat wave that might have happened back in the 50s, is going to be a lot hotter now," Francis said. "Another aspect that we see connected to climate change but that you don't hear about as much is the fact that there is also a lot more water vapor in the atmosphere now. As we warm the oceans and warm the air, there is more evaporation, and that water vapor makes us feel hotter."

Water vapor is what creates the heat index, which is the combination of temperature plus how much moisture is in the air. A rising heat index means dangerous conditions for the young, elderly or others whose health may already be compromised. The National Weather Service advises people to drink plenty of water; stay out of the sun and in air-conditioned rooms; and to check on relatives, neighbors and the elderly.