PHOENIX (AP) - Paramedics summoned to an Arizona retirement community last summer found an 80-year-old woman slumped inside her mobile home, enveloped in the suffocating 99-degree heat she suffered for days after her air conditioner broke down. Efforts to revive her failed, and her death was ruled environmental heat exposure aggravated by heart disease and diabetes.

In America’s hottest big metro, older people like the Sun Lakes mobile home resident accounted for most of the 77 people who died last summer in broiling heat inside their homes, almost all without air conditioning. Now, the heat dangers long known in greater Phoenix are becoming familiar nationwide as global warming creates new challenges to protect the aged.

From the Pacific Northwest to Chicago to North Carolina, health clinics, utilities and local governments are being tested to keep older people safe when temperatures soar. They’re adopting rules for disconnecting electricity, mandating when to switch on communal air conditioning and improving communication with at-risk people living alone.

A 2021 study estimated more than a third of U.S. heat deaths each year can be attributed to human-caused global warming. It found more than 1,100 deaths a year from climate change-caused heat in some 200 U.S. cities, many in the East and Midwest, where people often don’t have air conditioning or are not acclimated to hot weather. Another study showed that in coming decades dangerous heat will hit much of the world at least three times as hard as climate change worsens.

Older people of color, with a greater tendency for chronic conditions like diabetes, obesity and high blood pressure are especially at risk.

An undetermined number of older people died during the summer of 2021 when an unexpected heat wave swept across the U.S. Pacific Northwest. Canada reported that coroners confirmed more than 600 people died from the heat in neighboring British Columbia.

Many U.S. cities, including Phoenix, have plans to protect people during heat waves, opening cooling centers and distributing bottled water.

But many older people need personalized attention, said Dr. Aaron Bernstein, who directs the Center for Climate, Health.

“If you are elderly and sick you are unlikely to get into an Uber or bus to get to a cooling center,” said Bernstein, who vividly recalls a 1995 heat wave that killed 739 mostly older people in Chicago, his hometown. “So many were socially isolated and at tremendous risk.”

Sociologist Eric M. Klinenberg, who wrote about the catastrophe in his book “Heat Wave: A Social Autopsy of Disaster in Chicago,” has noted social contacts can protect older people during disasters.

“Older people are more prone to live alone,” he said, “and they are the most likely to die.”

Chicago encourages residents to check on older relatives and neighbors on hot days and city workers visit people’s home. But last year’s deaths at a Chicago apartment house shows more is needed.

Bernstein’s center is working with relief organization Americares to help community health clinics prepare vulnerable patients for heat waves and other extreme weather. A “climate resilience tool kit” includes tips like making sure patients have wall thermometers and know how to check weather forecasts on a smartphone. Patients learn simple ways to beat the heat, like taking a shower or sponge bath to cool off and drinking plenty of water.

Alexis Hodges, a family nurse practitioner at the Community Care Clinic of Dare in coastal North Carolina, said rising temperatures can cause renal failure in patients with kidney problems and exacerbate dehydration from medications like diuretics.

Utility companies can also help protect vulnerable people by halting power disconnections during hot periods.