Interactive Map Shows Link Between Redlining and Heat Exposure

Earlier this summer, Earth experienced its warmest day on record. As temperatures continue to rise, extreme heat has become a growing public health risk. More than 1,200 people are killed by extreme heat each year in the US alone. As with other climate risks, vulnerability to extreme heat varies based on where you live. And in the US, some of that risk can be tied to historical redlining ratings from the Home Owners’ Loan Corporation (HOLC).

This interactive dashboard explores the relationship between heat exposure and redlining. Created by the Science Museum of Virginia and Esri, it relies on research from Hoffman et al. (2020) that compares heat across redlined neighborhoods.

The dashboard includes neighborhoods for nearly 150 cities across 30 states. For each city, you’ll see neighborhoods labeled with their ratings from the HOLC. Ratings ranged from A (best) to D (hazardous), with D ratings often assigned to areas with larger Black populations in the 1930s and 1940s. On the map, neighborhoods are shaded based on how current temperatures compare to the city overall. Areas in red experience more heat than the city average, while blues represent areas that are cooler.

Across the map, 94% of cities see higher temperatures in D-rated neighborhoods than A-rated neighborhoods. D-rated neighborhoods are an average of 2.6 degrees Celsius (4.48 degrees Fahrenheit) warmer than A-rated neighborhoods. Neighborhoods with D ratings were historically seen as less desirable and suffered from underinvestment. These temperature variations are just one example of the effect of these ratings.

The dashboard includes more data to show the present-day impacts of redlining. You can explore tree cover (which reduces heat) and impervious surfaces (which reflect heat) for each neighborhood. You can also learn more about home values, vacancy rates, and demographics. Taken together, it becomes clear how these 80-year-old ratings from the HOLC still impact communities today. Places with A ratings tend to have lower temperatures, more green space, and higher home values than those with a D rating.

Mitigating extreme heat and its impacts won’t be easy. Maps like this show where specific communities may be more vulnerable. But they also show where investments in efforts like tree equity or cooling centers could have the biggest impact.