Florida tops nation in dangerous risk of heat and humidity, study finds

As climate change warms the planet, you can bet Florida will feel the heat.

The sunshine state, according to a study released Wednesday by Climate Central, tops the nation in the number of metro areas expected to see a dangerous combination of heat and humidity, driving heat index temperatures to 104 degrees.

By 2050, all 13 cities on the list, including Miami, Tampa, Naples and Vero Beach, will see 100-plus days a year of the miserable mix that can cause a host of health problems and even death — meaning more weather that feels like South Florida’s last few sticky, searing weeks.

Miami also comes in first for the number of days expected to top 90 degrees, with nearly twice as many as the next in line, sizzling McAllen, Texas.

“Heat is already the number one weather-related killer in the U.S. It’s not floods or hurricane or tornadoes,” said Alyson Kenward, an author of the report and a senior scientist at Climate Central, a nonprofit news organization staffed by scientists and journalists.


“These hot and sticky conditions have already been increasing since the 1970s and in the future, if greenhouse gas emissions continue at the rate they’ve been going, we’re going to see more and more dangerous heat conditions,” she said.

Just last week, the National Weather Service issued its first heat advisory for South Florida in seven years. The warning came on the heels of the warmest June on record for the contiguous U.S. since 1933. Last year also ranked as the warmest on record for the planet, beating out the previous winner: 2014.

So what’s causing the increasing heat? Kenward said as greenhouse gases increase, temperatures rise causing the atmosphere to hold more moisture, particularly in summer. Since 1970, the study found summers have warmed in 45 of the lower 48 states. The study also found the summer dew point had increased in 87 percent of the 200 major cities examined in the last 45 years.

That combination of heat and humidity can make temperatures feel hotter than they actually are, a lethal mix that at 104 degrees is dubbed a danger day. On danger days, cooling off can be harder, leading to sunstroke, heat exhaustion and other conditions. The young and the elderly are particularly susceptible to danger days.

In the future, as the planet warms, the number of dangers days will likely rise, the study found. Looking at 29 different global models, Climate Central found the average number of days would increase in 360 of the nation’s biggest cities. Half those with the biggest increase are in Florida, with Cape Coral and Fort Myers leading the pack. On average, the state now sees about 25 such days a year. By 2050, that number could be as high as 130, the study found.

“Where Florida really came to the top in our analysis is the change and how many more days we’re going to see,” Kenward said. “In a state like Texas, they’re already having a lot of hot days, whereas there’s not as many days in a city like Miami. All of a sudden when temperatures increase, the number of days where you hit that danger point is going to be way up.”

Follow Jenny Staletovich on Twitter @jenstaletovich