HOUSTON – When the torrential rain stopped on Friday afternoon, Ms Laura Lowry could see the steam rising off the wet pavement. She was on her front porch in the Fifth Ward neighbourhood of Houston, desperate for relief from the relentless humidity and 32.7 deg C heat. The air-conditioner in her house worked, but she and her husband, reliant on disability cheques, could not afford to run it.

The lack of cool air was not 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 past 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 the coming week, with heat indexes rising to well over 37 deg C across a vast swathe of the South, reaching from Texas, across the Gulf Coast and into Florida.

It has created misery, and has also underscored a recognition that 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 Dr 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 ageing process makes older bodies generally less capable of withstanding extreme heat, doctors say.

“They’re at extremely high risk of heat stroke and death,” Dr 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 heatwaves, most of the deaths occur in the homebound elderly.”

In many communities, including in New Orleans and Houston, officials have opened cooling centres and shelters in recent weeks, with air-conditioned shuttle buses meandering through neighbourhoods, picking people up. Programmes are also in place to provide or repair air-cons 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 Mr David Flores, 81, who lives in an apartment in Miami’s Little Havana neighbourhood. The temperature there approached 32 deg C on Friday, but the heat index – a measure of what the temperature actually feels like – ranged from 40 to 42 deg C. With a single wall air-con unit in his apartment, he said: “I leave the bedroom door open so that it cools down my little living room.”

Mr 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 heatstroke, a person’s body temperature will spike, reaching 39.4 deg C or higher. “The patient is going to stop sweating entirely,” he said, and could lose consciousness.

“That’s a 911 emergency,” he said. “You’re now dealing with heatstroke. Your mortality rate is now approaching 50 per cent.”

Familiarity with the heat has led to strategies for coping. Ms Nati Guerrera, 88, of Miami, emerges from her house only at night. Ms Virginia Rivera, 77, monitors the palm trees at her retirement community in downtown Orlando, Florida.

“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.” NYTIMES