Here’s where Miami ranks on a list of America’s ‘urban heat islands’

Miami is one of the hottest concrete jungles in the country, according to a report released this week by the nonprofit research group Climate Central.

That ranking is based on something called the “urban heat island effect.” Basically, it measures how temperatures rise higher in cities where the natural landscape has been replaced with densely packed buildings that trap heat. Generally, the effect is more intense in neighborhoods with bigger buildings and fewer trees, like Brickell or downtown, than it is in leafy suburbs like Coral Gables or Pinecrest.

The Miami metropolitan area has the third-worst urban heat island effect out of the 44 biggest U.S. cities, according to the Climate Central report. Only New York City and San Francisco trap more heat than Miami.

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That means local residents who are already sweating through record-breaking summer heat have to deal with even higher temperatures every time they walk down the street.

“Cities are being disproportionately impacted by this heat,” said Kaitlyn Trudeau, a senior research associate at Climate Central. “With climate change, we’re already seeing increased extreme heat. This is exacerbating that.”

On average, temperatures in the Miami metro area — which, for the purposes of this study, covers a roughly 150-square-mile area that stretches from Westchester to Miami Beach and Hialeah to South Miami — are 8.3 degrees hotter because of the urban heat island effect, according to the Climate Central report.

Those findings fit with another study published this month which concludes that many parts of Miami-Dade County get far hotter than the official temperature reading found on weather apps or newscasts. Researchers at the University of Miami, Florida International University and others placed thermometers in parts of the county known to have intense urban heat island effects and found that maximum temperatures were, on average, 6 degrees higher than the official reading taken from the weather station at Miami International Airport.

Urban heat magnified in Brickell

In the hottest parts of Miami, the urban heat island effect can crank up the temperature as much as 12 degrees, according to the Climate Central report.

Miami leads the country in terms of the percentage of its population that lives in neighborhoods with 12 degrees or more of urban heating: More than 12,000 people, representing 1.5% of the Miami metro area’s population (as defined in the study), are feeling that level of heat.

Nearly all of them are in heavily built-up parts of Brickell or Edgewater according to the report, which shows the heat island impact for each U.S. census tract in the Miami metropolitan area. Those areas are home to dense skyscrapers and don’t have many trees to offer shade.

Earlier this year, Miami-Dade County mayor Daniella Levine Cava pledged to prioritize 15 “areas of concern” in the county’s tree-planting efforts to reduce the urban heat island effect. These neighborhoods have tree canopies that cover less than 20% of the ground with shade and a poverty rate over 20%. They are: Opa-locka, Brownsville, Gladeview, West Perrine, Naranja, West Little River, Goulds, Pinewood, Hialeah, Westview, Norland, Carol City, Lake Lucerne, Scott Lake and Bunche Park.

In areas with little shade and high poverty, vulnerable residents — including people who are elderly, pregnant, disabled or homeless — face higher risk of heat-related illness. That’s especially true for residents who are living without air conditioning during a sweltering summer that has seen record-breaking daytime temperatures and nights when the air fails to cool.

Reducing the urban heat island effect

Miami can bring down the temperature by easing the urban heat island effect, said Trudeau.

“The biggest thing we can do is replace surfaces that absorb heat with surfaces that reflect heat,” said Trudeau.

That includes painting roofs white, using light-colored or reflective pavements, and making more room for parks and swales instead of cement and asphalt. Planting more trees to shade streets and homes can also offer some relief.

Miami-Dade County officials have pledged to plant enough trees to cover 30% of the ground with shade by 2030, up from the current figure of about 20%.

This climate report is funded by Florida International University, the Knight Foundation and the David and Christina Martin Family Foundation in partnership with Journalism Funding Partners. The Miami Herald retains editorial control of all content.

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