So, how hot is Charleston really? City grappling with climate change joins heat study

Years ago, on the question-and-answer website Quora, someone asked, “How hot does it get in Charleston?”

“Go into your bathroom and turn on the shower as hot as it can go. Then close the bathroom door. Sit in there for an hour. That is June-September,” a local in the Southern city typed back.

Soon, on a summer’s day in sweltering heat and humidity, the hunt for a more precise answer will get underway.

Charleston is the first city in South Carolina selected to participate in a federal program to map out temperature hot spots.

When the mapping is complete, the data collected during a single summer day by a team of community members will be able to show exactly how hot it gets in the Holy City and also how those temperatures vary by neighborhood.

Already, data show it isn’t getting any cooler: Charleston is expected to have triple its current number of extreme heat days by the end of the century.

“The history of Charleston is that people left the city in the summertime, and they went either to the mountains or the Northeast to escape. That is not necessarily the case today. With more residents moving here today, we need to understand how great the heat threat really is,” said Mark Wilbert, Charleston’s chief resilience officer.

Temperature disparities among parts of town may also reveal deeper inequities.

Past studies have shown that within the same city, some neighborhoods can be up to 20 degrees hotter— and that often it is low-income communities of color that bear the brunt of scorching heat.

In densely populated areas with fewer trees, more concrete buildings and large paved surfaces it tends to be hotter than other parts of the city.

“There’s injustice that’s built up around heat, just like flooding,” said Scott Curtis, director of The Citadel’s Lt. Col. James B. Near Jr. Center for Climate Studies.

“A lot of people who live in public housing and low-cost areas don’t have those trees, that shade, those amenities you would expect to see in other neighborhoods. Instead, there are large parking lots and concrete buildings,” Curtis said. “And if you’re in an area with a lot of asphalt and impervious surfaces, it can make an already hot day even hotter.”

Led by the National Oceanic and Atmospheric Administration (NOAA), the heat mapping project this summer will document the hottest parts of cities in 11 states across the country.

Along with Charleston, heat mapping will take place in Albuquerque, New Mexico; Atlanta; New York City; Kansas City, Missouri; Raleigh and Durham, North Carolina; San Diego; San Francisco; as well as parts of New Jersey, Indiana, Massachusetts, and Virginia.

“Our Nation faces a growing climate crisis that has exacerbated inequities, particularly for the low-income and communities of color,” U.S. Secretary of Commerce Gina M. Raimondo said in a news release about the national effort, which also hopes to identify where action is needed to protect vulnerable populations.

This will be the third summer for the Heat Watch initiative.

To do this work, at least 22 community volunteers will fan out across 10 square miles of the city. Led by a team of local partners, community members will use heat sensors mounted onto cars or bikes as they travel around the city. They’ll collect data morning, afternoon and evening to show how heat changes throughout the day.

Already, nine partner organizations have signed up to participate in the effort with the city, including The Citadel’s climate center and various Medical University of South Carolina offices, including its institute for air quality studies, office of health promotion and its sustainability office.

Janice Barnes, co-founder of Climate Adaptation Partners, said heat is a public health issue.

“Heat kills 20 times more people than hurricanes, and we don’t talk about it,” Barnes said.

Statistics from the National Weather Service show extreme heat kills more Americans than any other weather event. But unlike hurricanes, Curtis said, people are not ordered to evacuate from a heat wave.

Wilbert said now is the time to take a closer look at heat, especially as the city considers policy surrounding land-use and how it decides to build moving forward.

In some ways, heat was always a factor in how Charleston developed and functioned. Proof of it can still be seen today on the peninsula.

Before the advent of air conditioning, historic homes in downtown were built facing south to capture the cooler breezes coming off the waters in the hot summer climate. Today, a universally accepted indicator of a blisteringly hot day in Charleston is when the city orders horse carriages be pulled off the streets.

“This is about what we can do to make sure we build for the future,” Wilbert said.

Cities from past campaigns have used the heat maps to inform heat-mitigation decisions, educate residents and identify areas for further research on solutions. In Houston, for example, the city used its mapping results in a climate action plan.

An exact date for the heat mapping has not been set, but Wilbert estimates it will take place sometime in late July or early August, times when heat indexes historically spike in Charleston. On Friday, members will meet to discuss possible routes.