We mean literally. Minneapolis was divided by strict racial covenants, with neighborhoods where people of color could obtain loans and buy homes, and others where they explicitly couldn't.

Redlining has since been outlawed, but not much has changed. Today, the city’s black and brown residents are still mostly clustered in the same areas they were historically relegated to, and the city’s most affluent areas have remained overwhelmingly white. (Check out the outstanding Mapping Prejudice project for more info.)

Where you live determines a lot about how the rest of your life is going to go, including access to jobs, transit options, where your kids go to school, property value, and the potential to accrue familial wealth—even whether you feel comfortable walking down the street.

As it turns out, it can also mess with your life in a very physical way: devastating urban heatwaves.

Not everyone experiences the same hot summer days. Different neighborhoods within the same city can vary in temperature by as much as 20 degrees (Fahrenheit). These “heat islands” usually have fewer green spaces and less tree coverage, making them scalding patches of concrete pavement. And a recent study by Portland State University researchers found they line up eerily with those old housing covenants.

After taking a look at the hottest areas in 108 cities, researchers discovered formerly redlined neighborhoods can run about 13 degrees hotter than their non-redlined counterparts. Minneapolis’ own temperature difference was on the high end at 11 degrees. Here’s a handy graph from the study, tweeted by local urban blogger William Lindeke.

Redlined neighborhoods in Minneapolis are over 10º warmer than the rest of the city. https://t.co/FqCLRAs1GU pic.twitter.com/egFtq2po1d — William Lindeke (@BillLindeke) January 13, 2020

“This systemic pattern suggests a woefully negligent planning system that hyper-privileges richer and whiter communities,” author and urban studies professor Vivek Shandas said. “As climate change brings hotter, more frequent, and longer heatwaves, the same historically underserved neighborhoods… will face the greatest impact.”

That’s going to be particularly important to us here in Minnesota, one of the fastest-warming states in the nation. Some parts of the state are between 1 and 3 degrees hotter than they were a century ago, and spates of extreme heat are becoming more common. Minneapolis also happens to be one of the nation’s fastest-warming cities.

In cases of truly high temperatures, where you live might become a matter of life and death. Between 2000 and 2018, heat-related illness accounted for 56 deaths in our state, according to the Minnesota Department of Health—and as the department has pointed out, it’s probably going to get worse.