When the torrential rain stopped on Friday afternoon, Laura Lowry could see the steam rising off the wet pavement. She was on her front porch in the Fifth Ward neighborhood of Houston, desperate for relief from the 91-degree heat. The air-conditioner in her house worked, but she and her husband, reliant on disability checks, couldn’t afford to run it.
The lack of cool air wasn’t simply a matter of discomfort for Ms. Lowry, 73. It was dangerous. Just a few weeks ago, there had been a terrifying moment when she was so taxed by the heat after waiting outside a food pantry that she had slumped into her porch chair as soon as she got home. “I couldn’t make it inside,” she said. “I felt like I was passing out.”
Another wave of dangerous heat sweeping across the South and into the West this week has posed particular perils for older people, who are among the most vulnerable to such extreme conditions.
Forecasters expect the scorching spell to continue through next week, with heat indexes rising to well over 100 degrees across a vast swath of the South, reaching from Texas, across the Gulf Coast and into Florida.
It has created misery, and has also underscored a recognition that the health risks stand to intensify as a changing climate brings higher temperatures that will likely endure for longer periods.
“This can be deadly, especially in these vulnerable populations,” said Natalie Christian, an assistant professor of geriatrics at the Tulane University School of Medicine in New Orleans.
“I certainly don’t think it’s a problem that is going to go away,” she added. “It’s something we’re going to have to respond to, and we’re going to have to respond to in a bigger way.”
The aging process makes older bodies generally less capable of withstanding extreme heat, doctors say.
“They’re at extremely high risk of heat stroke and death,” James H. Diaz, a professor of environmental and occupational health sciences at Louisiana State University’s School of Public Health, said of older people. “When we look at what happens with these heat waves, most of the deaths occur in the homebound elderly.”
In many communities, including in New Orleans and Houston, officials have opened cooling centers and shelters in recent weeks, with air-conditioned shuttle buses meandering through neighborhoods, picking people up. Programs are also in place to provide or repair air-conditioners or help people struggling to afford their electricity bills.
But in some of the South’s hottest places, there was a sense on Friday that the heat was inescapable.
“There’s nothing we can do about this heat, only God can do something,” said David Flores, 81, who lives in an apartment in Miami’s Little Havana neighborhood. The temperature there approached 90 degrees on Friday, and the heat index — a measure of what the temperature actually feels like — ranged from 105 to 109 degrees. With a single wall unit in his apartment, he said, “I leave the bedroom door open so that it cools down my little living room.”
Victor Hugo Grajales, 66, said he was trying to avoid leaving his air-conditioned home in Miami. “Young people can handle this, they have the energy,” he said. “But seniors are suffering.”
Older bodies tend to hold more heat than younger ones, and as people age, they produce less sweat, making it tougher to regulate body temperature and dissipate heat. “It can be harder for even healthy older adults to tell if they’re dehydrated or overheated,” Dr. Christian said.
Common health issues — including heart problems, high blood pressure and diabetes — put older people more at risk of consequences from heat stress, medical experts said. Medications also have an effect: Certain drugs can increase the amount of heat generated in a person’s internal organs, influence the amount of heat that a person can tolerate or interfere with sweating.
Signs of heat stress include feelings of exhaustion and possibly a headache, dizziness and flushed skin. “Your skin may be moist and clammy, your pupils are dilated,” Dr. Diaz said. “You may be sweating a little bit but not enough.”
If a situation is progressing to a heat stroke, a person’s body temperature will spike, reaching 103 degrees or higher. “The patient is going to stop sweating entirely,” Dr. Diaz said, and could lose consciousness.
“That’s a 911 emergency,” he said. “You’re now dealing with heat stroke. Your mortality rate is now approaching 50 percent.”
Euradell Williams, 71, underwent a triple bypass surgery last year and has diabetes. She knows the heat affects her blood pressure. She tries to be cautious, but living on the south side of Houston means the heat is unavoidable, especially as she takes the bus most days to a community center more than an hour away, where she does crafts, swims in the indoor pool and socializes.
“By the time I leave here I’m drained,” she said at the center on Friday. “I’m just slumped over on the bus after just a minute of being out there.”
Familiarity with the heat has led to strategies for coping. Nati Guerrera, 88, of Miami, only emerges from her house at night. Virginia Rivera, 77, monitors the palm trees at her retirement community in downtown Orlando, Fla.
“You see the trees blowing in the breeze, you can go out and enjoy it,” said Ms. Rivera, who has a heart monitor and recently suffered a stroke. “If you open the door and the trees aren’t moving, stay inside.”
This year’s especially intense heat “causes aches and pains,” she noted, adding, “It just cuts your air and you can’t breathe.”
In another neighborhood of Orlando, Veronica King, 67, said she keeps her air-conditioner running even if she can’t afford to. “I have to figure out how to cover that bill,” she said, adding that she relies on machines that help her breathe. “When it’s hot, I can’t breathe.”
In Houston, where the heat index could reach 107 degrees on Sunday, Ms. Lowry and her husband, Jasper, 72, have come up with a compromise. They have two cars, neither with working air-conditioning. But they figured they could at least spare the money to repair it in one of them.
“I used to get out here and work in the yard, and trim the grass and work on the car,” Mr. Lowry said, sitting in the wheelchair he has needed since having a stroke. “But I can’t do it no more because it’s too hot.”
He stayed outside, watching over the man he had hired to fix his car, waiting for the chance to turn it on and — at last — feel a blast of cool air.
Abigail Geiger contributed reporting from Orlando, and Verónica Zaragovia from Miami