This article was first published by WJCT News, and is republished here with prior written permission of the authors.

An excerpt from “Warming Brings Muggier Weather to Jacksonville, Threatening Most Vulnerable” By Brenden Rivers and Ayurella Horn-Muller.

Even before the summer, Jacksonville’s average temperature between Jan. 1 and April 30 was 65.1 degrees, the city’s warmest start to the year since 1971, putting outdoor workers and other vulnerable groups at risk of heat stroke.

The Climate Change Threat

This particularly muggy summer fits with a broader trend — the combination of high levels of heat and humidity, which can be deadly, is getting worse in Florida and beyond.

‘Humid heat’ is another name given to an index for measuring heat that’s important for human health — the wet bulb temperature. Like the heat index, wet bulb temperature measures how heat, moisture and other elements affect the body. If humidity levels get too high when temperature is also extreme, sweating becomes physiologically impossible, which can lead to deadly heat stroke.

Scientists at Columbia University, Loughborough University and NASA published a paper in May revealing the rapid pace with which extreme wet bulb temperatures have been worsening globally, concluding it won’t be long before humans can no longer survive in some parts of the Middle East and South Asia.

In Florida, the frequency with which the muggiest days occurred each year was found to have increased by 75% over a 20-year period, adding to health risks in an already-muggy state.

NASA postdoctoral researcher Colin Raymond — one of two authors of the study, published in the journal ScienceAdvances — said one of the most surprising findings was the severity with which the combination of heat and humidity impacts coastal regions like Florida.

“It was always sort of assumed on some level that the lower temperatures along the coast and the higher humidity was sort of offset when it came to heat stress,” said Raymond. “But just looking at the most extreme events in the last 40 years, there are certain coastline areas [like much of Florida] where that is not the case.”

Cranking Up The Heat In The Sunshine State

For the ScienceAdvances study, the scientists used earth modeling to examine humid heat data from 1979 to 2017 around the world. Then, working with Climate Central analysts, the team calculated state-by-state changes in the Lower 48, analyzing the frequency of the most extreme wet bulb temperature days by U.S. location. They discovered humid heat in Florida — on the hottest and most humid day of every year — has become substantially more intense.

A professor of meteorology at Florida State University, Vasu Misra has been studying humid heat along Florida’s coast. He said the findings are in line with other research, and work is under way to project future conditions as intensifying heat and humidity collide.

“It may come as somewhat of a surprise to some of us that in a coastal region like Florida, heat stress could still be a threat, because people think of sea breezes,” Misra said. “But the humidity is so high that the body is unable to cool down.”

A year after his brush with extreme heat, Seabrooks is working in real estate. But he also describes himself as an urban farmer, which means he still exerts himself outside. When he does, he said, he’s working for himself and on his own terms.

An atmospheric and marine scientist at the University of Miami, Amy Clement suspects what people are experiencing may be even more extreme than what Raymond’s study is suggesting, because of potential problems with weather station data across urban areas.

“This entire year in South Florida has been record-breaking in incredible ways, by a large margin. And that includes heat and humidity,” Clement said, pointing to the effects of climate change caused by pollution from fossil fuels and other industrial activities.

“The issue of heat in Florida has been dismissed by experts for a long time,” Clement said. “I think it’s because they think that we’re adapted to high heat. But two things — one, the study is arguing that there are limits to that adaptability, and two, we’re adapted to high heat because of air conditioning.”

This story was produced through a partnership between WJCT and Climate Central, a nonadvocacy science and news group.

(Source: Rivers, Brenden, and Ayurella Horn-Muller. “Warming Brings Muggier Weather to Jacksonville, Threatening Most Vulnerable.” WJCT News, WJCT and Climate Central, 8 July 2020,

(Image Source: Occupational Safety and Health Administration)

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