Western United States swelters amid deadly heat By Tim Gaynor PHOENIX (Reuters) - A dangerous, record-breaking heat wave in the western United States contributed to the death of a Nevada resident and sent scores of people to hospitals with heat-related illnesses. The scorching heat, caused by a dome of hot air trapped by a high pressure ridge, pushed the mercury above 100 F (38 C) in parts of California, Arizona, Idaho, Colorado, Nevada and Utah and Texas. Paramedics in Las Vegas, where searing temperatures reached an all-time high of 118 F (48 C) on Saturday, found an elderly man dead in his apartment, which had no air-conditioning. The unidentified man had prior medical issues and "either the heat got to him or the medical condition was aggravated by the heat," Las Vegas Fire & Rescue spokesman Tim Szymanski said. Scores of other people were treated for heat-related symptoms, including a man who pulled off a Nevada highway and called 911 to say he felt ill after driving for several hours without air-conditioning. He was hospitalized in serious condition with heat stroke, Szymanski said. Cities and towns across the sun-scorched western United States opened air-conditioned "cooling centers" in community centers, homeless shelters and libraries, and warned residents to avoid prolonged exposure to the high temperatures. It's like when you open up the door to your oven and you get that blast of hot air. That's kind of what it feels like outside," said Charlotte Dewey, a weather service meteorologist in Phoenix, Arizona, where temperatures nudged 114 F (46 C) on Sunday. "It's pretty dangerous, even for people who are very acclimated to the weather, to be outside and doing physical activity ... we advise everybody to avoid being outdoors," Dewey added. In Los Angeles County, many people have been hospitalized or treated for dehydration, exhaustion and heat stroke, a fire department spokesman said. There were fears that migrants attempting to cross into the United States from Mexico would die in the desert. More border agents were added on the American side, said Brent Cagen, a spokesman for the Tucson sector of the U.S. Border Patrol. At least three people who attempted to illegally cross the border into Arizona were found dead this week, likely succumbing to the heat, Cagen said. Firefighters worry about dry conditions, which have ignited several major brush fires across the region recently, and about more blazes ignited by wayward fireworks launched from backyards to commemorate the Fourth of July holiday. Reporting by Jane Sutton in Miami, Brad Poole in Tucson, Timothy Pratt in Las Vegas and Marty Graham in San Diego; Editing by Doina Chiacu and Stacey Joyce