PHOENIX (AP) -- Scorching heat radiated across the U.S. Southwest on Tuesday, setting record highs in California's Death Valley, Thermal and Palm Springs in a week that forecasters say could prove to be the region's hottest this year.
The National Weather Service said a new high of 127 degrees (52.7 Celsius) was set at California's Death Valley. Weather service forecaster Chris Outler in Las Vegas said the record broke the previous one of 126 (52 Celsius) registered for the day in 1916.
He said Las Vegas reached a high of 112 (44 Celsius) on Tuesday, but that wasn't a record for the day.
The weather service said other record highs set Tuesday included 122 (50 Celsius) in Thermal, in California's Coachella Valley, and 121 (49.4 Celsius) in Palm Springs.
Forecaster Andrew Deemer said the Phoenix high of 116 (46 Celsius) on Tuesday was tied with the previous record set in 2014.
Arizona and parts of California, Utah and Nevada remained under an excessive heat warning with the heat wave continuing later into the week. Forecasters extended the excessive heat warning for Arizona's Grand Canyon through Thursday, with highs in the South Rim area expected in the low 90s.
"The hottest weather of the year will persist the next several days with near record highs for many locations," the National Weather Service in Phoenix said. "After this period of hot and dry weather for the majority of the area, better moisture will arrive back into the region late in the week."
The weather agency uses a complicated formula that varies from region to region to declare an excessive heat warning, including close to record or record-breaking temperatures.
In California, power grid operators called for cutbacks in electricity usage as parts of the U.S. Southwest dealt with another day of scorching heat.
With triple-digit temperatures forecast across the region, the California Independent System Operator Corp. urged people to ease off blasting air conditioners or using washing machines or other appliances during the peak power usage times of 5 p.m. to 9 p.m. Tuesday and Wednesday.
The Los Angeles County Department of Public Health also urged people to stay out of the sun.
"When temperatures are high, even a few hours of exertion may cause severe dehydration, heat cramps, heat exhaustion and heat stroke," said Dr. Jeffrey Gunzenhauser, the county's interim health officer.
Children, the elderly and pets shouldn't be left in homes without air conditioning or in cars even with open windows because temperatures can quickly soar to life-threatening levels, he said.
With some of the highest Southwest temperatures over the next few days expected in Phoenix, officials cautioned people to stay hydrated and take advantage of cooler indoor buildings.
"Nationwide, heat is the #1 heat-related killer," the weather service in Phoenix said on its website.
"Another very hot day is in store for Arizona with high temps at or above record levels," the weather service office in Tucson said in a tweet. "Drink plenty of water and limit your time outside."
Maricopa County public health officials say 155 people died in the Phoenix area last year from heat-caused illnesses such as heat stroke.
Spokeswoman Jeanene Fowler said Tuesday there have been five confirmed heat-associated deaths in Maricopa County this year, with the cause of another 34 deaths still under investigation.
"The numbers are definitely under what they were at the same time last year, so that's a positive sign," Fowler said.
Elsewhere in the western U.S., the hot, sunny weather prompted officials to raise the fire danger at Yellowstone National Park in Wyoming to a high ranking for the first time this year.
The high ranking comes after lightning sparked the first wildfire of the season near Yellowstone. No special restrictions were placed on campfires at the park.