BOISE, Idaho (AP) – Sweltering residents across the West headed for lakes and rivers on Thursday, seeking relief from triple-digit temperatures expected set records through at least today.

Some office workers were given the option to float on innertubes down the Boise River instead of sitting at stuffy desks, with temps in Boise expected to reach 105 degrees. Forecasters predicted a high of 107 today – six degrees higher than the 101 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 to avoid any outdoor activity except during the cooler early morning hours. Phoenix was expected to reach 115 degrees; forecasters predicted a high of 123 degrees in Baker, Calif.

In St. George, Utah, a high of 115 was predicted for Thursday, just two degrees shy of the state’s all-time temperature record set in 1985. St. George Police Sgt. Craig Harding has been giving out heat safety tips to residents in radio announcements and in a column he writes for a local newspaper. But some still aren’t paying attention.

“Unbelievably, on Monday we actually responded to a call of a child locked in a car,” he said. “If we find a kid in that situation, they’re going to get a ticket for child neglect.”

Around Las Vegas – where temperatures reached 109 degrees before 1 p.m. Thursday – 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.

In Montana, farmers anxiously watched their crops and thermometers. High temperatures for a handful of days can harm crop yield.

“Prolonged heat is devastating. Four or five days of it is going to be hard,” said wheat farmer Lynn Nordwick near Poplar, Mont.

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 was expected to reach 93 degrees Thursday, and 92 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.

“For some people, we’re the only affordable alternative for a place to cool off,” Dey said.

In Spokane, Wash., the temperature was expected to soar past 100, breaking a record for July 5 set in 1975. In the northern Idaho lake city of Sandpoint, a forecast temperature of 103 would break a record for the date set in 1926, the National Weather Service said.

Northeastern Oregon residents were experiencing what was expected to be the hottest day of the year on Thursday, with temperatures hitting 107 in Hermiston and Pendleton.

The heat and a dry spring raised concern among firefighters.

“We’re really primed to burn right now,” said Dennis Winkler, an assistant fire management officer for the Wallowa-Whitman National Forest. “We’re well above average in terms of fire danger for this time of year.”

An index that helps fire officials estimate how fast flames would spread was at its highest point for early July in the past decade, said Dave Quinn, who manages an interagency dispatch center at the La Grande Airport in Oregon.

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.