To most, the upcoming cool weekend weather should be refreshing if not pleasant. To some, it could be deadly.
On Friday, the lows are expected to drop into the 40s, and even that can cause hypothermia in vulnerable people, such as the elderly, children, those with medical conditions such as diabetes and those who imbibe or take certain drugs.
"Cold weather in Florida can affect some as much as hot weather does," said Palm Beach Fire Rescue Capt. Don DeLucia. "We just have a shorter window with cold weather."
Hypothermia is a decrease in a person's core body temperature, shutting down normal functions and potentially leading to death, medical authorities say. Adding to the danger, it settles in gradually with no glaring symptoms.
Hypothermia aside, cold weather also can be deadly because many people improperly use space heaters, which can spark fires, said Mike Jachles, spokesman for Broward Sheriff Fire Rescue. Or, he said, people try to warm their homes using appliances such as toasters, stoves and ovens.
A better solution, he said: "We tell people to layer or stay with a relative who has central heat."
To warn residents of cold dangers, the weather service issues wind chill advisories when "feels-like" temperatures are forecast to reach 35 degrees or lower and when readings are forecast to fall to 25 degrees or colder.
"It's really meant for the population at large, and hypothermia is the main concern," said meteorologist Robert Molleda.
Most healthy people aren't affected until exposed to temperatures in the 30s for four hours or more. Yet every time a cold wave hits, fire rescuers across South Florida usually respond to one or two hypothermia victims — usually homeless or elderly people — on average, about 10 per winter.
Compared to other kinds of emergency calls, hypothermia cases are relatively rare, even in Palm Beach County, where temperatures tend to be 5 to 10 degrees colder than Broward and Miami-Dade counties.
Since 1979, the condition has killed more than 120 people statewide. In one episode alone, in December 1989, 26 people froze to death statewide, including six in South Florida, according to National Weather Service records.
Because they frequently don't have enough blankets and warm clothes, the homeless are most vulnerable to hypothermia. They can be left out in the cold even when county agencies deem the weather isn't chilly enough to open shelters.
Broward County opens its shelters when wind chill readings are forecast to fall to 45 degrees or lower for at least three hours. Palm Beach County opens shelter when temperatures are forecast to fall to 40 degrees or wind chill readings are predicted to drop to 35 degrees or lower — for at least four hours.
Mary Blakeney, assistant operations manager for Palm Beach County Emergency Management, said that policy was established several years ago by a county committee that included social agencies and homeless organizations.
She said the policy is based on statewide standards and isn't intended to discourage homeless people from settling in Palm Beach County.
"We don't necessarily only shelter homeless in cold weather," she said.
Blakeney added the committee meets annually and could end up easing the policy. "Public safety is our number one concern," she said.
Hypothermia also can result from cold water. Taking a quick dip in the ocean or a pool usually isn't dangerous. However, falling into a cold canal and being unable to climb out can be fatal, said Dr. Robert Hasty, an assistant professor of internal medicine at Nova Southeastern University.
"Water really decreases body temperatures precipitously," he said.
People who have more muscle mass and body fat are better able to defend against cold, said Dr. Laurence Gardner, professor of medicine at the University of Miami School of Medicine.
He said mild hypothermia occurs when a person's body temperature falls below 95 degrees and severe hypothermia when it falls below 82 degrees. At 68 degrees, the brain stops functioning.
"Once you get somebody who's very confused or disoriented, has blueness of the skin and a decreased pulse, then you're in a very serious situation," Jachles said.
Gardner said it's completely untrue that Floridians are more vulnerable to cold because they have "thin blood."
"That's an old wife's tale," he said.
firstname.lastname@example.org or 954-572-2085.