But it's not just Phoenix, or even the Southwest: It's hot in most of the country.
"It's been steamy from the Gulf Coast all the way to New England, featuring afternoon thunderstorms throughout the region," says CBS News Meteorologist George Cullen.
A week-long heat wave has hit California's San Joaquin Valley, reports CBS News Correspondent Jerry Bowen. One farm worker is dead from heat exhaustion there. And in Los Angeles, three men nearly suffocated in the closed car in which they were sleeping.
Thirteen illegal migrants have died in the Arizona desert in the last four days and the Border Patrol is finding more victims needing help.
Since Saturday, Phoenix police reported a dozen people had died of apparent heat-related illnesses. Ten were homeless; the other two were elderly women, including one whose home cooling system wasn't on.
By comparison, the Arizona Department of Health Services documented 34 deaths because of heat-related illnesses among all Arizona residents last year. The number of illegal immigrants killed by heat-related illnesses are counted separately.
Phoenix has endured above average temperatures every day since June 29, with the high expected to reach 112 degrees on Tuesday. Even during the coolest part of the day, the mercury failed to descend lower than 91 degrees.
The elderly are especially vulnerable.
"It's really awful. It's just taking all my strength," one woman told CBS News.
The spike in deaths prompted the mayor on Monday to ask for water donations. The city has only a two-day supply of bottled water to hand out, reports Bowen.
Bill Manson, development coordinator for Central Arizona Shelter Services, said a number of companies and individuals had been donating water and organizing drives to collect bottled water.