ALBUQUERQUE, N.M. — The Southwestern U.S. is bracing for another week of blistering temperatures, with forecasters on Monday extending an excessive heat warning through the weekend for Arizona’s most populated area, and alerting residents in parts of Nevada and New Mexico to stay indoors.

The metro Phoenix area is on track to tie or to break a record set in the summer of 1974 for the most consecutive days with the high temperature at or above 110 degrees Fahrenheit (43 Celsius). Even the morning low temperatures are tying historic records.

Along the U.S.-Mexico border, federal agents reported that extreme temperatures over the weekend contributed to 45 people being rescued and another 10 dying.

With so many consecutive days of excessive heat, forecasters, physicians and local health officials throughout the Southwest are recommending that people limit their outdoor exposure and know the warning signs of heat illness.

Knowing the Signs

From heavy sweating and dizziness to muscle spasms and even vomiting, experts say heat exhaustion and heat stroke are likely to become more common. In coming decades, the U.S. is expected to experience higher temperatures and more intense heat waves.

Heat stroke is the most serious heat-related illness and happens when the body loses its ability to sweat.

The skin gets hot and red, and the pulse quickens as the person’s body temperature climbs to 103 F (39 C) or higher. Headaches set in, along with nausea, confusion and even fainting.

Jon Femling, an emergency medicine physician and scientist at the University of New Mexico, said the body tries to compensate by pumping blood to the skin as a way to cool off. And the more a person breathes, the more they lose fluids, becoming increasingly dehydrated.

Important electrolytes like sodium and potassium also can be lost when sweating.

“So one of the first things that happens is, your muscles start to feel tired as your body starts to shunt away,” he said. “And then you can start to have organ damage where your kidneys don’t work, your spleen, your liver. If things get really bad, then you start to not be perfusing your brain the same way.”

Experts say it’s important to recognize the signs of heat stroke in others, as people may not realize the danger they’re in because of an altered mental state that may involve confusion.

In the case of heat stroke, experts suggest calling 911 and trying to lower the person’s body temperature with cool, wet cloths or a cool bath.

With heat exhaustion, the body can become cold and clammy. Other signs include heavy sweating, nausea, muscle cramps, weakness and dizziness. Experts say the best thing to do is to move to a cool place, loosen clothing and sip some water.

Older people, children and those with health conditions can face greater risks when the temperatures are high.

During extreme heat events, one of the most common ways people can die is from cardiovascular collapse, experts said, because of the extra energy the heart has to expend to help the body compensate for the hot temperatures.

In general, health officials say staying indoors, seeking air-conditioned buildings and drinking more water than usual can stave off heat-related illnesses. Caffeine and alcohol are no-nos. Eating smaller meals more often throughout the day can help.

Learning the Limits

Researchers at Arizona State University are trying to better understand the effects of extreme heat on the body and what makes hot weather so deadly.

They’re using a special thermal mannequin called ANDI that is outfitted with nearly three dozen different surface areas that are individually controlled with temperature sensors and human-like pores that produce beads of sweat.

“A lot of research that I and my colleagues do is just really focused on understanding how people are responding to higher levels of extreme heat over longer periods of time and then what we can do about it,” said Jenni Vanos, an associated professor at ASU’s School of Sustainability.

There are 10 thermal mannequins in existence, with most used by athletic clothing companies for testing. ASU’s manikin is the first that can be used outdoors thanks to a unique, internal cooling channel.

The university also has developed a new “warm room,” or heat chamber where researchers can simulate heat-exposure scenarios from around the globe. Temperatures can reach 140 F (60 C) inside the room — and wind and solar radiation can be controlled for experiments.

Vanos said measuring short- and long-wave radiation in the environment can also tell researchers how much a surface — or a person — in a specific location of a city would heat up.

“And so under these extreme conditions, what’s going to really be able to be modified or changed within the urban environment is shade,” she said. “In a place like Phoenix or really any sunny hot area, shade is a really critical factor to be able to reduce that overall heat load of the human body.”

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Finding Relief

While air conditioners are cranked up and fans are blowing full blast, residents across the region are anxiously awaiting the start of the monsoon season, hoping it will help to keep the heat at bay.

But so far, the summer thunderstorms — which usually bring cloud cover, lightning and downpours to the Southwestern desert — are absent due to the ongoing El Niño weather pattern, National Weather Service meteorologist Sam Meltzer said.

“It looks like things are going to be abnormally dry over the next couple of months,” Meltzer said, noting that storms that might break the heat depend on wind patterns drawing moist air from the Gulf of California into Arizona, New Mexico and Nevada.

“But that doesn’t mean we aren’t going to get thunderstorm activity,” Meltzer said. “It just might be delayed.”

Meltzer worked in Phoenix before transferring last winter to Las Vegas. He noted that while temperatures rose last month in the Phoenix area, June stayed abnormally cool in southern Nevada.

The official daytime temperature at Harry Reid International Airport in Las Vegas remained below 100 F (37.8 C) for a record 294 days before temperatures reached 102 F (38.9 C) on June 30. The previous record of 290 days, from 1964 to 1965, had stood for 58 years.

Still, it’s not just the air temperature that people need to worry about, Vanos said. Humidity can make it more difficult for the body to produce sweat as a way to cool off.