Sweltering residents across the West headed for lakes and rivers yesterday, seeking relief from triple-digit temperatures expected to set records through at least today.

One firm's office workers were given the option to float on inner tubes down the Boise River instead of sitting at stuffy desks, with temperatures in Boise reaching 103 degrees yesterday afternoon. Forecasters predicted a high today of 107 - six degrees higher than the 101 record for this date set in 1985.

But temperatures in part of the West were climbing so high that authorities warned residents of southern Nevada, southeast California and northwest Arizona that outdoor activities could be dangerous except during the cooler early-morning hours. Phoenix reached 115 degrees; Baker, Calif., reached 125.

A 1-year-old boy was found dead Wednesday evening in a locked car in temperatures approaching 100 in Orofino, Idaho. He had been locked in the car for about five hours when passersby noticed him, and the boy's stepgrandmother was charged in his death, authorities said yesterday.

Comment: Without conscience. Yet another victim of psychopathy.

St. George, Utah, hit 115 by 5 p.m., a day after a nearby sensor recorded an unofficial reading of 118, which would top the state's record of 117 set in St. George in 1985. Summer temperatures across Utah are running 10 to 15 degrees above normal, meteorologist Brandon Smith said.

"As far as temperatures, for as far out as we can see, there's no relief," he said.

Around Las Vegas - where temperatures reached 116 yesterday afternoon - transformers overheated and caused electrical-pole fires because of all the people switching on air conditioners, said Scott Allison with the Clark County Fire Department.

Even Stanley, Idaho, which at more than 6,000 feet elevation is routinely the coldest place in the lower 48 states, was seeing record highs, the National Weather Service said. The remote town in the Sawtooth Mountains reached 91 degrees yesterday, and was expected to hit 92 today.