Some Baltimore blocks could be 15 degrees hotter than others. Mapping them could help address heat hazards.

Volunteers log temperatures while driving through the city in an effort to help NOAA as it is conducting research on urban heat islands in Baltimore. (Amy Davis. Baltimore Sun video)

Temperatures in Baltimore officially peaked at 98 degrees Wednesday. But some city blocks might have baked at temperatures as much as 10 to 15 degrees higher.

In the high heat of the afternoon, a team of researchers and volunteers crisscrossed the city in cars equipped with temperature sensors to find out just how hot it gets, and where.


The data are being used to create a detailed map of the pockets of Baltimore where an abundance of blacktop and a lack of tree cover create what are known as urban heat islands.

Twenty-five people have died from heat-related deaths this year, the deadliest season in at least the last five years.

The National Oceanic and Atmospheric Administration, which is funding the project, hopes to duplicate it around the country next summer to show where heat is a serious health hazard, and where cities and states could be doing more to protect those who live there.


Heat exceeding 95 degrees is expected to become twice as frequent over the next dozen years, researchers said, so the heat islands also offer a preview of the extreme weather threats they believe will eventually be widespread. There already is evidence to suggest temperatures can vary by as much as 16 degrees from a city’s coolest spots to its hottest.

“Now is the time to be having these conversations about, are we willing to tolerate the risk in this kind of heat exposure?” said David Herring, a program manager in NOAA’s climate science office. “If not, what do we want to do about it?”

The heat is already taking lives. Maryland health officials said Wednesday that 25 people have died of heat-related illnesses across the state this year, the most they have reported in at least five years, and five times as many as in 2017. About half those deaths have occurred in Baltimore.

Hot, humid air is flowing into the Baltimore region this week, bringing high temperatures into the mid-90s and a heat index in excess of 100 degrees, at times.

As the heat climbed Wednesday, the nearly 20 volunteers fanned out in nine cars with instructions to traverse a wedge of the city from precisely 3 p.m. to 4 p.m., during what is typically the hottest hour of the day. To get the best readings, they were instructed to not drive faster than 40 mph, and to keep moving at above 5 mph as much as possible.

Protruding from the passenger windows of each car were PVC pipes containing thermocouples, which use electric voltage to measure temperature. Each thermocouple was connected to data recorders collecting temperature data every second for an hour.

Sheila McMenamin cranked down the window of her Honda Civic and attached the device onto her window, like a sports team’s flag, only without the flag. She set out from her home in Remington to explore a swath of Northwest Baltimore that includes the shade of Cylburn Arboretum but also the scorching expanse of parking lots surrounding Reisterstown Road Plaza.

As director of programs for the Baltimore Tree Trust, she said she was interested in the research to get a better sense of how the heat can vary from block to block — and where more trees are most needed. The nonprofit has planted 5,500 trees since 2008, mostly in East Baltimore, but is looking to spread that canopy into western and southern parts of the city.

“It was pretty noticeable,” she said of the differences in landscape and, likely, temperature. “It made you really feel for folks who were walking around or waiting at bus stops.”

Jeremy Hoffman and Vivek Shandas, the researchers overseeing the project, expect to compile their data and create a map within a couple of weeks. They’ve done it before — in nine cities including Portland, Ore., Albuquerque, N.M., Hong Kong and Doha, Qatar. They sent out a team in Washington on Tuesday.

In Richmond, Va., where Hoffman is a climatologist at the Science Museum of Virginia, the scientists found some of the most stark evidence of urban disparities — both in terms of temperature and other socioeconomic indicators. In one leafy park along the James River, their thermocouplers measured 87 degrees one afternoon last July; a few miles away, along a four-lane roadway, it was 103 degrees.

Around the hotter area, they found a higher concentration of poverty, and of 911 calls for heat-related illnesses.

“That big difference was really shocking for us to find out,” Hoffman said. “This is an environmental justice issue.”


Hoffman and Shandas met in Oregon, where Shandas is an urban studies professor at Portland State University and where Hoffman studied as a graduate student in paleoclimatology. They used funding from the National Science Foundation and other sources to begin researching urban heat islands.

NOAA hopes the scientists can use the data from Baltimore and Washington to show that the research can be duplicated in cities across the country. NOAA tasked them with conducting this study for $30,000, then writing up a report on how it could be repeated elsewhere for less money.

Herring said he hopes the information can help guide where cities might decide to whitewash pavement, install green roofs or open cooling centers.

Dr. Leana Wen, Baltimore’s health commissioner, said the data could be very helpful in Baltimore. She said she expects to see that heat has the most severe impacts in city neighborhoods already distressed by sudden infant deaths, lack of access to healthy food, and high rates of cancer and heart disease.

“It affects those who are already the most vulnerable,” Wen said. “Heat waves are becoming more common, lasting longer and becoming more severe. The effects of those heat waves will be worse in urban areas like ours.”

The research was expected to continue into Wednesday night and Thursday morning, when the drivers were being asked to pass along the same routes at 7 p.m. and then 6 a.m. By Thursday afternoon, storms are expected as a cold front brings a break from the heat.

But until then, Wen warned that risks of heatstroke and heat exhaustion remain elevated — she extended a “Code Red” heat alert through Thursday.

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