Summer Days Often Feel Much Hotter If You Live In One Of California’s Historically Redlined Neighborhoods

California’s triple-digit heat is back — and new research shows residents in the state’s most underserved neighborhoods suffer the most when the mercury rises. 

Portland State University’s heat-mapping project tapped volunteers last summer in four California metro areas to attach GPS-equipped temperature collection gadgets to their cars and drive along set routes for an hour in the morning, afternoon and evening. They drove through the Bay Area, Los Angeles, Victorville and Sacramento. 

The research project was led by Vivek Shandas, a professor who believes this form of heat-data collection can help city planners solve decades-old problems.

“We’re trying to bring the understanding of climate change and the changes happening on a planetary scale down to the individual person and down to the individual city block,” Shandas said.

He says the old way of measuring the temperatures by satellite doesn’t provide an accurate picture of what people are feeling at street level. 

“What you’re getting [with satellite] is rooftops, tops of trees, not the lived experience of what you and I standing in this park would actually experience,” Shandas said.

Sacramento Heatmap

Data-collection took place in Sacramento on August 14, one of the hottest days of 2019 in Northern California. I joined other volunteers for the experiment. 

But while they were driving their predetermined hour-long routes, I was bicycling along the streets and paths of Sacramento to collect data from areas where cars can’t go.

The temperature swing was palpable as I rode from the city’s busy J Street near Sacramento State to the adjacent American River Trail. It was also easily felt when riding from sunny to shady streets.

The data collected that day indicates the temperature differentials between neighborhoods can vary by as much as 20 degrees. 

Wealthy, tree-canopied neighborhoods are typically cooler, and low-income, asphalt-heavy communities run hotter.

Experts like sociologist Dr. Jesus Hernandez say decades of urban-planning decisions are to blame for this disparity.

He pointed to Highway 99 as an example: It separates a historically underserved community from one of Sacramento’s wealthiest enclaves.

“You see this freeway that we have here, because this is exactly the line of where race covenants stop — Oak Park, Curtis Park,” Hernandez said. 

He grew up in Oak Park when it was — as he describes it — one of the most dangerous places to live in the state. The highway serves as a barrier between rich and poor, a function he says was not an isolated nor accidental decision.

“It was designed by race, all of our freeways were,” Hernandez said.

The result was a north-south corridor of poverty and race through Sacramento, where asphalt and concrete won out over the city’s famous tree canopy. 

It shows up in the heat data, too: redlined communities of color run on average six degrees hotter than the rest of the region, according to Shandas

“Areas that were historically redlined from 1920 to [the] 1960s, 93 percent of the cities were hotter on average than cities that weren’t redlined,” Shandas said.

In order to fix these inequities, a new state project is working on heat-island problems in Sacramento and a few other cities. 

Louise Bedsworth oversees the project, called Transformative Climate Communities, and she says Fresno is getting the first big chunk of money to protect low-income communities against rising temperatures.

“We’re investing $66.5 million,” Bedsworth said. The money will go toward affordable housing, businesses, eco-friendly transportation and a new community college satellite campus — all with more cooling trees and greenery.

“It reduces the heat-island effect, but also makes it more likely that people can bike and walk and be outside and play,” Bedsworth said.

The funding comes from the state’s cap-and-trade program, because the projects are also designed to reduce greenhouse gas emissions.

In its first two rounds, the program has funded projects in Ontario, Watts, Pacoima, and Sacramento. A third round of funding is expected in June. As of late May, there was no funding set aside in Gov. Gavin Newsom’s latest budget proposal for TCC funding beyond the third round.

Those who study the issue say there are hundreds of these heat-island communities in California, and temperatures are only expected to climb in the years to come.

Correction: A previous version of this story incorrectly stated the funding for projects in Ontario, Watts, Pacoima. Those have been funded through the program's second round.