Sweltering residents across the West headed for lakes and rivers, seeking relief from high temperatures expected to set records through at least Friday.
Some office workers were given the option to float on innertubes down the Boise River instead of sitting at stuffy desks, with temperatures in Boise reaching 104 degrees (40 degrees Celsius) Thursday afternoon. Forecasters predicted a high of 107 F (42 C) on Friday - six degrees higher than the 101 F (38 C) record for that date set in 1985.
"Once it gets that high - 105, 107, 109 - it just feels hot," said Rick Overton, a copywriter who arranged the float trip for the digital marketing firm Wirestone. "I'm going to keep a tube under my desk for the whole summer and whenever it gets this hot I'm going to escape."
But temperatures in part of the West were climbing so high that authorities warned residents of southern Nevada, southeastern California and northwestern Arizona that outdoor activities could be dangerous except during the cooler early morning hours. Phoenix reached 115 degrees (46 C); Baker, California, reached 125 degrees (52 C).
A 1-year-old boy was found dead Wednesday evening in a locked car in temperatures approaching 100 degrees (38 C) in Orofino, Idaho. He was locked in the car for about five hours when passers-by noticed him, and the boy's stepgrandmother was charged in his death, authorities said Thursday.
Around Las Vegas - where temperatures reached 116 degrees (47 C) Thursday afternoon - transformers were overheating and causing electrical pole fires because of all the people switching on their air conditioners, said Scott Allison with the Clark County Fire Department.
Even Stanley, Idaho, which at more than 6,000 feet (1,800 meters) elevation is routinely one of the coldest places in the U.S., was seeing record highs, the National Weather Service said. The remote town in the Sawtooth Mountains reached 91 degrees (33 C) Thursday, and was expected to hit 93 degrees Friday.
Hardly anyone in the tiny town has air conditioning, said Nancy Anderson, Stanley deputy city clerk. The City Hall offices are also without that amenity.
"They're all going to the lakes and the rivers and trying to find the shade," Anderson said.
At least 150,000 people were expected to flock to the Lake Mead National Recreation Area in Nevada and Arizona in hopes of cooling off in the water this weekend, said Roxanne Dey, recreation area spokeswoman.
The heat wave began last week after a large high pressure center developed over Arizona, said National Weather Service forecaster Paul Flatt in Boise. A weather pattern was pushing that high-pressure center north into Canada, Flatt said, but most of the West is expected to experience high temperatures into next week.