PHOENIX, Ariz. -- It's a day like today when Phoenix truly earns the name the Valley of the Sun -- a day when even hardened desert dwellers say: it's just too hot.
"A heat wave isn't really a good way to describe it. It's more like a heat attack!" one jogger told CBS News.
That's when heat warnings take on added urgency.
"People can go right from what they think is heat exhaustion to symptoms of a heat stroke, which is actually a fatal illness," said Captain Reda Bigler, a paramedic with the Phoenix Fire Department.
The hottest it's ever been in Phoenix is 122. This week, that record is in jeopardy. It will be even hotter on Tuesday. Phoenix has only hit 120 degrees three times in recorded history.
The heat wave is also threatening to set records across the region including Tucson and Las Vegas.
Even the normally cool San Francisco airport reached 97 on Sunday. Its all-time record is 103.
The heat is also being. One near Brian Head, Utah, has destroyed one home and is threatening several others.
And California's bountiful winter snowpack is now melting so rapidly that the Kings River near Fresno is flooding, and forced more than 300 evacuations.
During the peak heat Tuesday evening, American Airlines had already cancelled around 40 flights because some small planes can't safely take off when it's above 118.