The scorching hot weather was expected to continue in the West on Sunday — after reaching 118 degrees in Phoenix — and other parts of the U.S. from Illinois to the lower Mississippi Valley.
The temperature in Phoenix broke a 10-year record of 116 for the city, where about 4,000 homes in the metropolitan area were without power — and air-conditioning — after a monsoon brought wind gusts that toppled power lines.
Maricopa County Sheriff Joe Arpaio ordered thousands of bags of ice to the county's outdoor jails, saying inmates could have as much as they want and for any use — including to sit on.
Santa Barbara County planned cooling centers in libraries, senior centers and other community facilities in seven cities.
The high temperatures were expected to continue Sunday, remaining well into the 100s, with some areas of the Southwest pushing above 110 degrees, according to The Associated Press. Human body temperature is about 98 degrees.
The National Weather Service issued heat advisories for the San Francisco Bay areaand for parts of Illinois and Missouri.
The Bay area notice warned the elderly, the very young and the infirm to avoid spending too much time outdoors.
"Individuals who fall into this categoy should be especially careful by drinking plenty of water and seeking a cooler location for the day if no air conditioning is available in your living quarters," it said.
The advisory was due to be in effect from 12 p.m. to 9 p.m. PT Sunday, with temperatures expected to range from the 90s to 105.
The Illinois/Missouri heat advisory was due to be in effect until 7 p.m. CT. Temperatures were expected to reach about 100 for the fourth straight day, which the NWS said would result in a greater chance of heat-related illness because of the cumulative effect.
Over 120 in Death Valley
The Weather Channel reported that temperatures could be up to 15 degrees above average in parts of the Southwest, with highs during the day from the 90s across central and eastern Montana to more than 120 degrees in California's Death Valley.
Temperatures were expected to range from the upper 90s to more than 100 degrees from the lower Mississippi Valley to the southern Plains, the Weather Channel said.
It warned isolated thunderstorms would begin to develop from the mountains of Southern California to parts of Colorado, New Mexico, Utah and Arizona, where a large wildfire has been burning for days, threatening the Los Alamos nuclear laboratory.
"A few of these storms could produce damaging wind gusts in Arizona. Unfortunately, lightning could ignite more fires," Mark Ressler, lead meteorologist at the Weather Channel, said.
He also said thunderstorms were expected to hit Montana and "could turn severe with damaging wind gusts and large hail."
Skiers in bikinis
Amid the warnings and fear the heat could make people sick, skiers were donning shorts, bikini tops and Hawaiian shirts.
Ski resorts from California to Colorado opened for the weekend to take advantage of an unusual combination of dense lingering snow from late-season storms in the Sierra Nevada and the Rockies and a high-pressure system ushering in warm air from the east.
Resort operators were reporting large crowds, balmy temperatures and plenty of bare skin.
"I've seen bathing suits, funny costumes like Hawaiian skirts and silver sequined pants. Shorts are very standard today," said Rachael Woods, a spokeswoman for California's Alpine Meadows, which has offered Independence Day skiing just one other time in its 50-year history. "People are coming off the slopes and putting on flip-flops."
The weather at the base of the mountain was in the upper 50s.
At Snowbird Ski and Summer Resort in Utah, 783 inches of snow this season smashed the old record of 688 inches set in the winter of 1983-84.
By the time the resort closes for the season after Monday's holiday, it will have been open a record 202 days.
Colorado's Arapahoe Basin Ski Area drew more than 1,500 skiers and snowboarders Saturday — about half as many people as a regular-season weekend day, said spokeswoman Leigh Hierholzer.
The resort, located 70 miles west of Denver, last offered skiing on Fourth of July weekend in 1997, she said.
The weather allowed some of the more adventurous skiers at Arapahoe to try "pond skimming," a blend of snow skiing and waterskiing in which an individual picks up as much speed as possible going downhill and then attempts to coast over the top of a mid-mountain lake.
Storm kills child
In Wisconsin, an 11-year-old girl was killed and 39 other people were injured when a fierce thunderstorm swept through a rural county packed with holiday campers, toppling hundreds of trees and leaving several thousand utility customers without power.
Authorities said most of those injured in Burnett County were treated and released, but three were in critical condition Saturday evening.
Heavy winds upended boats in the area and blew them ashore, while an airport hangar in neighboring Douglas County collapsed onto a single-engine plane.
The storm came at one of the worst times of the year for rural Burnett County: A summer holiday weekend, when the area's lakes and rivers attract tens of thousands of visitors, said Rhonda Reynolds, a regional director for Wisconsin Emergency Management.
The county population is 17,000 she said, but the long weekend drew an estimated 80,000 visitors to the county about 90 miles northeast of Minneapolis.
This article includes reports from The Associated Press and The Weather Channel.