HOLLYWOOD, Fla. — After an estimated 215 people died in hospitals and nursing homes in Louisiana following Hurricane Katrina in 2005, policy makers realized that the nation’s health care institutions were ill-prepared for disasters.

One of the rules they created after years of discussion looked especially prescient in light of the tragic deaths on Wednesday of eight nursing home residents in Florida’s post-hurricane heat. But the rule, regarding power supplies and temperature control, does not take effect until November, and even then, some patient advocates are concerned that it does not go far enough.

The debate shows how challenging it has been to overhaul health care rules even after repeated instances of power failures and flooding, from Katrina to Hurricane Sandy in 2012, to Hurricane Harvey last month and now Hurricane Irma. Hospitals and nursing homes have pushed back against some requirements, arguing that they are costly and unnecessary.

The new federal rule will require that nursing homes have “alternate sources of energy to maintain temperatures to protect resident health and safety.”

But the rule does not specifically require backup generators for air-conditioning systems — the nursing home in Florida, Rehabilitation Center at Hollywood Hills, did not have such a generator — and now some are questioning whether the rule should.

“It’s vague, but this event is going to highlight the need,” said Dr. David Marcozzi, an associate professor at the University of Maryland School of Medicine and former director of a federal health care preparedness program. “Let me put it this way, if you were in Alaska and what was required to maintain safe temperatures was a heater, you wouldn’t say you don’t need the heater.”

“No one should freeze to death,” he added. “No one should have a heat injury.”

A criminal investigation was continuing Thursday into the deaths of the residents, who ranged in age from 71 to 99, in a nursing home lacking air-conditioning because of widespread power failures from Hurricane Irma. The center had asked the power company, Florida Power & Light, to restore electricity, but nursing homes were not considered as high a priority for restoration as other facilities like hospitals.

Broward County and company officials have bickered over who set the priorities, while questions also remained about whether the residents should have been removed sooner. More than 140 were evacuated to local hospitals on Wednesday.

“I’m spitting mad,” said Vendetta Craig, whose mother, Edna Jefferson, 87, lived at the home. She went to check on her Thursday at Memorial Regional Hospital, and said she was recovering. “We throw our elderly away. They’re a cash crop.”

The nursing home had a generator, but it did not power the air-conditioning, which usually requires a much more powerful generator, or a second unit. Such a generator is not required by current rules — and it is unclear whether those enforcing the new rules will require it, either.

The nursing home was obligated to keep the temperature safe, and officials there said spot coolers and fans had been used after the power went out — though doctors and emergency workers who went in on Wednesday used words like “oven” to describe the conditions.

When it released the new rule, the Centers for Medicare and Medicaid noted that some people had wanted more clarity on the requirements. But the agency considered that facilities in one part of the country might have different demands than those in another. “We have not required minimums for these types of requirements because they would vary greatly between facilities,” the agency wrote.

As with many rules, cost is an issue, and homes that rely on Medicaid reimbursements say their thin margins make purchases like a second generator a daunting expense.

“That is not something you can go to Home Depot and pick up off the shelf,” said David Gold, the administrator of the Pinecrest Rehabilitation Center in North Miami. “The federal and state government should help us pay for it.”

But Keith Myers, chairman of the Florida Board of Nursing Home Administrators, said his company, MorseLife Health System, had purchased a $1.5 million generator five years ago for its 300-patient long-term care facility, and that it was partly covered by an adjustment in Medicaid’s reimbursement rate. “It’s not really an excuse,” he said.

Mr. Gold of Pinecrest said his generator had provided power for some portable air-conditioning units, the refrigerator and freezer and a lot of fans, but the primary air-conditioning unit was not working in the days after the storm. As the temperature in the facility neared 81 degrees, the threshold under the law, the home transferred its most fragile patients to other facilities.

The Florida governor’s office said Thursday that more than 150 assisted living facilities, as well as 44 nursing homes, had been evacuated or closed. Almost all of the state’s hospitals had power restored or were running on generators, the office said.

Florida was not the only state where nursing homes were under scrutiny. In Port Arthur, Tex., on Thursday, the police served a search warrant as part of an investigation into a nursing home that flooded from Hurricane Harvey.

After the storm, the police entered the home and found a foot of standing water, which was “chocolate brown” and filled with feces and urine, said Detective Mike Hebert. Patients were lying on beds in a hallway with water rising around them, he said. Helped by volunteers with boats, the police evacuated dozens of residents to safety.

“It took your breath away when you walked into the facility,” Detective Hebert said. “The pungent smell that everyone had to endure, especially the patients and the nurses.”

Bonnie Leonardo, whose mother, Loretta Linn, 83, was a resident of the Hollywood, Fla., nursing home, said that when the two spoke after the storm, her mother had reported that the air-conditioning was out, and that she was hot and not feeling well.

Ms. Leonardo, who lives in Texas, had purchased a fan for her mother a few years ago, and the home’s staff retrieved and set it up, she said.

Ms. Leonardo next received an update when she turned on the news Wednesday and saw reports of deaths at the home. Her mother survived and is recovering at Memorial Hospital.

In the past, Ms. Leonard said, “my mother has been treated wonderfully” by the home.

Now, she said, “I am so sick from this, I don’t even know what I’m doing.”