Meanwhile, in Las Vegas, high temperatures dipped below the 115-degree mark Wednesday for the first time in five days.
For the first time in years, Phoenix homeless shelters opened their doors during the day to offer respite from the blistering sun, which has delivered above-average temperatures every day since June 29. Police began passing out thousands of water bottles donated by grocery stores, and city officials set up tents for shade downtown.
"I don't know why I'm not burnt to pieces," said Chris Cruse, 48, after taking refuge in a shelter.
Four more bodies were found Wednesday, and Phoenix police officer Kathy Ralph tells CBS Radio News the death toll could rise.
"A couple of the people we found have been dead for awhile, and they're in that homeless environment, so it's possible that more could turn up," Ralph said.
Fourteen of the victims were thought to be homeless. Authorities did not know if a man found by the side of a road Sunday had a permanent residence.
The other three victims were elderly women, including one whose home cooling system was not on, police said.
"Most of us just run from air-conditioned box to air-conditioned box, so it's hard to imagine how omnipresent the heat really is for the homeless here," said Phoenix police Sgt. Randy Force.
In all of last year, the state Department of Health Services documented 34 heat-related deaths among Arizona residents. The number of illegal immigrants killed by heat-related illnesses while trying to cross the desert are counted separately.
The first deaths were reported Saturday. By Wednesday, the high still climbed to 109 degrees. Even during the coolest part of the day, the mercury has failed to descend lower than 89 degrees.
"In the mornings, about 9 or 10 o'clock, when it starts getting really hot, we just jump in and take a swim," he said. "The nights aren't much better. When the wind does blow, it feels like a blast furnace."
Both he and Cruse spent Wednesday at the Phoenix Rescue Mission watching movies in the shelter's chapel, which was opened Monday to anyone needing a break from the heat.
The shelter was also turning on hoses so transients could wet their clothes and had ordered 300 neckerchiefs that can be dipped in water and tied around the neck, said Bob Reed, a shelter manager.
Phoenix Mayor Phil Gordon said his office was asking Congress to provide utility assistance for soaring cooling bills the same way it provides for heating bills in Eastern states.
"Fair is fair. There are too many individuals dying of heat here," Gordon said.
Maricopa County, including Phoenix and its suburbs, has a homeless population between 10,000 and 12,000 people, said Gloria Hurtado, the city's human service director.
Emergency calls for heat stress in Las Vegas have averaged 15 to 25 a day for the past week, which is five to eight times the normal responses for paramedics, according to fire officials.
Authorities were investigating six deaths since July 14 to see if they were heat-related.
"You swim, you drink lots of water, and you hide, and you go out at night," Amanda, a bartender at the Golden Palms Casino, told CBS Radio News.
Thunderstorms were in the forecast for the next several days, raising the potential fire danger. Dry thunderstorms sparked a series of wildfires June 22, but forecasters predicted some precipitation with the pending storms.
The intense heat wave began July 12, when the city began a streak of nine consecutive 110-degree days. Las Vegas could tie an all-time record for most consecutive days if the high reaches 110 degrees on Thursday. But forecasters were predicting the city would miss the mark by one degree — hitting 109 for the high.
Las Vegas set multiple records Tuesday, the fourth consecutive day with temperatures of 115 degrees or higher. The previous record was three days.
Other records shattered Tuesday included the daily record high (117 degrees); daily average temperature (106 degrees); daily minimum temperature (95 degrees); number of days in a month when the high has been 115 degrees or higher (5).