By Brendan O'Brien and Rich McKay
(Reuters) -A searing heat wave that has settled over a coast-to-coast swath of the U.S. is expected to push temperatures on Wednesday as high as 110 degrees Fahrenheit (43 degrees Celsius) in parts of the Southwest, creating dangerous conditions for nearly 100 million Americans.
From Southern California to South Florida, residents are under excessive heat advisories, watches and warnings that may stay in place through the weekend, the National Weather Service said.
While stifling temperatures grip many parts of the country, Vermont and other Northeastern states began cleaning up from historic flooding triggered by intense downpours linked by climate experts to global warming.
The midday temperature in Las Vegas could climb to 108 degrees F (42 C) on Wednesday before challenging the desert city's all-time high of 117 F (47 C) on Sunday, the weather service said.
In Phoenix, Arizona, the high was expected to reach above 110 F (43 C) for the 13th successive day on Wednesday. The forecast puts the city's daily highs above 110 F at least through next Wednesday, which would shatter the record of 18 days above that mark set in June 1974.
At the family-owned Six Points Hardware store in Phoenix, fans and air conditioner units have been flying off the shelves, said store manager Drew Materniak.
The heat means "business is good," he said, noting the biggest seller has been large cooling fans, sold largely to businesses like auto shops where businesses can't air condition.
"Just stay inside man, just stay in side," Materniak said as his advice for dealing with the heat.
Forecasters urged people facing the extreme heat, especially children and the elderly, to keep out of the unrelenting sun, to reschedule strenuous outdoor activities and to drink plenty of fluids during the next several days.
Phoenix residents were under "extreme heat risk, (an) increase in heat related illnesses, including heat cramps, heat exhaustion, and heat stroke," the service warned. "Heat stroke can lead to death."
The blistering temperatures in the American Southwest were caused by a high ridge of stagnant air parked in the atmosphere, said Ashton Robinson Cook, a forecaster with the weather service's Weather Prediction Center.
That air blocks cooler air and storm systems from rolling through the area, so it's "just full sun and heat," he said.
In Texas, most will see temperatures in the upper 90s to above 100 F (37 C) on Wednesday, while the heat index will make it feel like 114 F (46 C) in some places through the weekend. Warm ocean water is causing the moist, humid air over much of the state that drives the heat index higher, Cook said.
"The problem with Texas is that the lows won't get below 80," he said, adding that there's little chance to cool off.
Many metropolitan areas, including Los Angeles County, the most populous in the nation, were opening cooling centers for those who cannot get out of the extreme heat on their own.
"There’s a heatwave coming! Follow these helpful tips to keep yourself, loved ones, and pets safe from extreme heat," Los Angeles County said on Twitter.
CLEANUP BEGINS IN VERMONT
The growing frequency and intensity of severe weather across the U.S. is symptomatic of global, human-driven climate change, experts in the field say.
In Montpelier, Vermont's capital, floodwaters turned the city's downtown into a swirling, brown waterway that damaged roads leading in and out of town and trapped some residents in their homes and businesses. At least 117 water rescues were carried out by teams across the northeast state as of Tuesday evening.
Catastrophic flooding that inundated the picturesque downtown may have compromised Montpelier's water supply, the city said on Facebook.
Officials told the city's 8,000 residents to boil their water before using it until further notice, and urged people to stay off the roads as cleanup crews assess the damage.
(Reporting by Brendan O'Brien in Chicago and Rich McKay in Atlanta; editing by Jonathan Oatis and Bill Berkrot)
