As this weekend's heatwave descends on the Bay Area, thirty volunteers are participating in a community heat mapping project — called Urban Heat Watch— as part of SF's effort to better understand and locate "heat islands" in the city.

The current climate conditions in the United States have caused an estimated 46% of Americans to endure at least three consecutive days of 100-plus-degree heat, on average, each year since 2010. This figure, however, is ballooning — and, by 2053, more than 100 million Americans may experience a heat index higher than 125 degrees Fahrenheit.

In San Francisco, our summers are traditionally cool and mild. (They've served as inspiration for viral tweets and source material for an entire New York Times article dedicated to our tepid summer temperatures.) But we're not immune to heatwaves, especially as the climate crisis worsens and threatens the existence of our famous marine layers that wrap the Bay Area in cool, dense fog.

To both find and learn more about areas in the city more prone to high heat, San Francisco has launched an on-the-ground effort to pinpoint how factors — like urban green spaces, tree canopy coverages, pavements, and buildings — can create neighborhood-level "heat islands" that drive health inequities.

"We're collecting on-the-ground data on how different neighborhoods experience heat and humidity, and when overlaid with what we know about where our vulnerable populations are located, will become a powerful tool to protect against extreme heat conditions," said City Administrator Carmen Chu in a press release; the City Administrator’s Office oversees initiatives to increase the City’s resilience to climate change, heat waves, and other challenges that impact social inequities. "This effort recognizes that heat doesn't impact our City's residents equally and as climate change continues to accelerate, helps us make smart and targeted decisions on where to invest in cooling centers, or even where to plant new street trees to cool down."

The Urban Heat Watch initiative, which is sponsored by the National Oceanic and Atmospheric Association (NOAA), aims to help San Francisco to respond better and more effectively to heatwaves. The thirty volunteers were tasked with installing heat sensors on their vehicles and drove 12 different routes across San Francisco neighborhoods at 6 a.m., 3 p.m., and 7 p.m. Friday, September 2nd.

Per the release, the vehicle-attached sensors collected neighborhood-specific heat and humidity data, which will inform future planning efforts. The pieces of data collected by the volunteers will then be extrapolated and used to create heat maps that will help the City understand how those aforementioned factors can create neighborhood-specific "heat islands."

These heat islands can exacerbate health issues with individuals suffering from pre-existing conditions and those unable to cool themselves properly indoors— a very real worry with just over 47% of the San Francisco Bay Area's households reported having air conditioning, per a 2019 U.S. Census Bureau's American Housing Survey.

"The City's most vulnerable communities do not have the resources to beat the heat, and lives have been lost due to extreme temperatures," said Eddie Ahn, executive director of Brightline Defense — an environmental justice organization that works in the Tenderloin, SoMa, Bayview-Hunters Point, and Chinatown — in the same release, noting that this week marks the anniversary of the 2017 Labor Day Weekend heat wave that saw parts of San Francisco hit 106 degrees Fahrenheit. "We are excited to be working with the City to map needs and identify resources that grapple with this new set of climate change disasters."

For additional information on San Francisco heat emergencies, visit

Related: Big Heat Wave Day on the Way

Photo: Getty Images/Sundry Photography