Dangerous ‘extreme heat’ days to multiply inSouth Florida, study finds. Who is at risk?

Yes, it’s already very hot in Miami-Dade County. But if climate change continues
unabated, South Florida could go from steamy to scorching, adding an extra month
of “extreme heat” days by mid-century.

That kind of extreme heat makes it hard to work — or live — outside and can sicken
or even kill people, particularly outdoor laborers, the poor and the elderly. That’s a
problem for Miami-Dade, which has more than 100,000 outdoor workers, the most in
the state. It also will make cooling homes, buildings and cars pricier.
A report released Monday from the nonprofit climate research group First Street
Foundation found that Miami-Dade leads the nation as the county that could see the
sharpest increase in dangerous hot days over the next 30 years, when the U.S. could
be an average of 3 degrees hotter.

The southeast, including Florida, is likely to see much higher temperatures more
frequently. That means extra weeks of the year where temperatures top 100 — or
even higher.

“It’s getting warmer there, and while it’s easy to say ’it’s already hot here,’ the
exposure to more dangerous days is what dominated the story in our report,” said
Jeremy Porter, First Street’s chief research officer.

The First Street report found that South Florida, including Miami-Dade, Broward
and Palm Beach, could see about 40 extra days a year where the heat index is over
100 degrees Fahrenheit. The region gets about 50 a year now. Heat index — also
known as the “feels like” temperature — factors in humidity with temperature.
These findings mirror previous studies’ projections of what global warming could
feel like for South Florida, a warning that pushed Miami-Dade to hire its first-ever
Chief Heat Officer, set up an extreme heat task force and conduct a heat
vulnerability study.
“It reinforces what we’re already planning for,” said Jane Gilbert, the county’s chief
heat officer. “The quality of life in Miami-Dade County in 30 years is highly
dependent on how globally we’re able to control greenhouse gas emissions. It’s
imperative that as a county and a state we are leaders on greenhouse gas emissions


That vulnerability report, published earlier this summer, is already guiding
investments. Researchers found that Miami-Dade has an average of 58 hospitalizations and 301
emergency department visits a year for heat-related illnesses. Deaths are harder to
count. In the five-year span, only two death certificates listed extreme heat as the
first cause of death.

Christopher Uejio, an associate professor at Florida State University and lead author
of the analysis, said that’s both because medical examiners have a high bar for
counting heat as the main cause of death and because “heat exacerbates such a long
list of health conditions that it’s hard to tease it out.”
In the analysis, researchers found that changing that standard to include all illnesses
that extreme heat would have worsened brought the total to 34 deaths a year.
As the county warms, those deaths increased. Every ten-degree increase in the heat
index led to an additional death a day, the study found.

“Without further adaptation, we could expect heat-related illnesses and deaths to
increase,” Uejio said.

From there, researchers took the risk factors for heat-related illness and death —
like poverty, whether people work outside or live in mobile homes or if they have
children — and mapped it out across the county.

The zip codes with the highest risk were in South Dade, Miami Gardens and the
Allapattah area.
Gilbert, the county’s heat czar, said she’s targeting these areas for tree planting and
preservation to keep them cool, and they’re first in line for the 360 new shaded bus
shelters the county is installing this summer.
They’re also the focus of the county’s heat season campaign of public service
announcements, billboards and presentations.

“We used the vulnerability assessment to focus our investments in boosting the
videos and social media posts and bus shelter ads in zip codes with the highest rate
of heat-related hospitalizations,” Gilbert said. “We’ve reached over a million
residents already in our campaign and we’re continuing at it.”


While researchers looked at a long list of factors that increase someone’s risk of
experiencing extreme heat, it boils down to two things: spending a lot of time
outside, usually while working, or living somewhere that isn’t properly cooled.

Miami-Dade has more outdoor workers than anywhere in the state, but there are no
laws at the state, national or local levels to protect them from heat stress.
The U.S. Occupational Safety and Health Administration has been slowly turning its
set of recommendations about offering laborers water, rest and shade into laws, a
multi-year process. In Florida, a bill that only recommended employers consider
offering some protections against heat stress (with no penalties for not doing so)
died after a single committee hearing, where it won unanimous, bipartisan

Miami-Dade is looking into proposing its own policy, Gilbert said. “We’re going to get the strongest possible policy that we can pass and hold. We have
to hope it won’t get pre-empted,” she said.

The other side of the equation is housing. Most apartments, condos and homes in
South Florida include air conditioning units, although it’s not standard in federally
subsidized housing. But running the AC is expensive, and as the cost of energy rises,
cash-strapped households often cut down on cooling to lower their bills.

One solution from the county is cooling centers or heat shelters. These are public
spots, usually community centers, parks and libraries, where residents can come
chill out during the hottest points of the day.

Ladd Keith, a University of Arizona Assistant Professor of Planning and Sustainable
Built Environments, said that these are helpful, but they don’t get at the real
problem of overheated housing.

“If the temperatures are still elevated in the evening, you’re essentially sending
those individuals back to unsafe conditions,” he said. “The root cause is we need
everyone to have a safe home to live in. The reason we need cooling centers in the
first place is we need everybody to have a safe place to live.”


If there is good news for Florida, heat waves and extreme temperatures aren’t as
common as they are in the western U.S. because of the cooling effects of the nearby
Atlantic Ocean and Gulf of Mexico.

“There’s almost a ceiling, a physical limit to how hot it can get because of the water,”
Porter said. “But there are a few places in Florida and along the Atlantic coast where
that protective effect is starting to diminish because sea surface temperatures are

Florida’s brand of heat risk can be more difficult to warn people about. It’s easier to
sound the alarm for a three-week heat wave or a two-day temperature spike than simply saying the whole summer will be sweltering.

Eyeing the potential health impacts of heat, Miami-Dade started announcing an
official heat season, which runs from May through October. It’s one more way to
warn residents about the kind of risk they face, since the threshold for a warning
from the National Weather Service is so high — a heat index of 108 degrees.

That doesn’t happen often. By the calculations in the First Street report, Miami-Dade
hit that figure zero times this year, and after another 30 years of warming, it’s
projected to hit that number just three times a year.

To solve that, Gilbert and the county worked with the local NWS office to come up
with lower thresholds to warn residents about heat risk. At a heat index of 103, the
NWS now talks about taking “extreme caution” in the heat in its forecasts.
“I think the NWS has always wanted to be mindful of not having to issue a heat
advisory or heat warning too often because people might disregard it,” she said. “It
currently shows that we have room to issue these kinds of advisories and still get
people’s attention.”

Published by Kat Duesterhaus

Digital Media Pro / Activist / Organizer

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