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, will not be enforced 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.”