San Francisco is known for its moderate climate. But as the global climate warms, the Bay Area is expected to experience more heat waves — and many residents lack an air-conditioned place to cool off.

“Because San Francisco is not a particularly hot city, all of our infrastructure that’s really developed for housing and office spaces is truly developed for cool coastal temperatures,” says Cecilia Mejia of Brightline Defense, an environmental justice nonprofit.

The group was part of a recent volunteer effort to map temperatures across the city to pinpoint which areas get hottest when the temperature rises.

Mejia says in general, neighborhoods on the west side are cooler because of the ocean breeze and more trees.

But the east side gets hotter because it’s more densely populated, with less shade. She says the east side is also home to more vulnerable people.

“Those are low-income communities. Those are communities that have been seen to have environmental justice issues,” she says.

The data the volunteers collected was shared with the city. Knowing which neighborhoods are most at risk will help city officials know where to set up cooling centers and plant more trees — so residents can stay safe as the climate warms.

Reporting credit: Ethan Freedman/ChavoBart Digital Media