July 2, 2013--Why the heat wave is so scary and what's behind it (Denver Post)

Excessive heat is the No. 1 weather killer in the United States, and it's at its most dangerous when it doesn't cool down at night. The current heat wave over California, Nevada, Arizona and New Mexico has temperatures hitting triple digits, with little relief at night. Hot weather is also baking the rest of the far West, including Washington, Oregon, Idaho and parts of Utah and Montana.

Q: What's so disturbing about this current heat wave?

A: It's unrelenting stubbornness. There is no relief at night. Phoenix set a record for highest nighttime temperature: 91. Las Vegas has gone three days without getting below 90, according to readings at the airport. "Nighttime heat is especially bad," said Eli Jacks, chief of fire and public weather services at the National Weather Service. "Not to get below 90 is crazy."

Q: What's so dangerous about that?

A: If you aren't in an air-conditioned place, "your body never has a chance to recover" at night, Jacks said. Normally the "feels-like" index — which factors in temperature and humidity — has to get to 80 degrees or below for your body to recover from the daytime heat, he said.

Excessive heat is the No. 1 weather killer in the United States, and it's at its most dangerous when it doesn't cool down at night. The current heat wave over California, Nevada, Arizona and New Mexico has temperatures hitting triple digits, with little relief at night. Hot weather is also baking the rest of the far West, including Washington, Oregon, Idaho and parts of Utah and Montana.

Q: How do heat waves compare to other weather killers?

A: In recent years, heat has been more deadly than other weather extremes in the United States. The Centers for Disease Control and Prevention indicate that on average, 658 people die each year from too much heat.

Q: Who is most at risk?

A: The elderly and children. The elderly make up 36 percent of heat deaths in the past decade, according to the CDC. And of all the excessive heat deaths, 69 percent are men.

Q: So what's causing all this?

A: Part of it is normal summer heat spurts, said meteorologist Kenneth James of the Weather Prediction Center in College Park, Md. But there's another fac