Excessive heat warnings in place for much of the U.S.

High temperatures turn dangerous in some places - NBC's Jay Gray reports

(NBC News/KYMA, KECY) - It's already mid-summer hot across much of the country, and the season doesn't officially start until this weekend.

"I mean it.. it.. really is hot over here." said Yuma's Angolie Ruiz.

In some places, triple-digit hot. Millions from coast to coast are now searching for ways to beat that heat.

"How do you feel? Are you cooling off?"
"Oh, absolutely."
"Yeah?"
"Absolutely."

The extreme conditions are no laughing matter for those who have to work outside.

"Anyone who is in the city working outdoors not in a climate controlled environment is absolutely at risk for heat stroke or heat exhaustion," said Battalion Chief Scott Clumpner with Dallas Fire Rescue.

Firefighters top the list. They're training in heat that, for now, doesn't come from flames.

"They work 24-hour shifts. So it is imperative for them to be acclimated to this," said Capt. Carlos Alcantar with Santa Clara CalFire.

Much of the work is in rugged terrain, and firefighters are loaded with gear.

"About 50-pounds. I have about 4-quarts of water at a minimum .. water weighs about 8-pounds a gallon .. I have a fusee.. files.. and my tools," said Jacob Williams, a CalFire firefighter.

Even hiking without that heavy load can be dangerous.

"You push it sometimes and it's just, you can't. Water, just definitely water and make sure you come early in the morning," said hiker Yolanda Ascencio.

Ascencio advises getting out before the sun, and the temperatures, get too high.