San Francisco activates heat mapping effort as City prepares for heat

Community members are collecting data to better understand how heat is distributed across San Francisco and help inform the City’s efforts to address health inequities related to heat waves.
September 02, 2022

SAN FRANCISCO, CA---Today, as San Francisco and the Bay Area prepare for high temperatures, more than 30 volunteers are participating in a community heat mapping project called Urban Heat Watch as part of the City’s efforts to address health inequities related to extreme heat. While city agencies with roles in heat emergency response prepare to respond to elevated temperatures, City leaders are also advising San Francisco communities to follow public health and safety guidance to stay safe and healthy during the heat. 

“I want to thank the NOAA and all of the volunteers today for partnering with our public health and safety departments on furthering our commitment to address the impacts of climate change,” said Mayor London Breed. “That includes mitigating the impacts of rising temperature on our communities with equity as our guiding principle. In past years, our City workers have stood ready and came together to utilize our public spaces like libraries and museums and staffed cooling centers where residents in need of access to them could have safe places during times of extreme heat. As we continue our part in working on environmental issues that affect our everyday lives, this partnership with the NOAA will help strengthen our work serving all of our communities and addressing the long-term and short-term impacts brought on by climate change.” 

The Urban Heat Watch initiative, sponsored by the National Oceanic and Atmospheric Association (NOAA), will help inform how San Francisco plans for and responds to heat waves. Volunteers are installing heat sensors on their vehicles and driving 12 different routes across San Franciso neighborhoods at 6am, 3pm, and 7pm today. As they drive, the sensors are collecting neighborhood-specific heat and humidity data, which will inform future planning efforts. The data collected by the volunteers will be used to create heat maps that will help the City understand how factors of our built environment, such as green space, tree canopy, pavement, 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 on 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.  "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 City Administrator’s Office oversees initiatives to increase the City’s resiliency to climate change, heat waves, and other challenges that impact social inequities. 

“Better understanding the role infrastructure plays in creating and addressing urban heat impacts is essential. Concrete, asphalt, and other urban surfaces absorb heat. Tall buildings can block wind and stifle air flow and often lack cooling mechanisms. Windows reflect and redirect sunlight. All of these factors influence the extent at which our communities experience heat which, in addition to social and economic factors, create unsafe conditions,” said Brian Strong, San Francisco’s Chief Resilience Officer. “The information collected from this project will help us understand how our built environment can reduce rather than exacerbate these impacts for all residents, but especially vulnerable populations.” 

“Extreme heat events reveal the public health inequities that exist in our city, leaving seniors, people with pre-existing health conditions, and those without access to cooling especially vulnerable,” said Director of Health, Dr. Grant Colfax. “We look forward to examining the data that Urban Heat Watch will provide to learn how we can better support those who are at higher risk.” 

This project is a cross-collaborative initiative bringing together City agencies—the Office of Resilience and Capital Planning, Department of Public Health, Department of Emergency Management, and Department of the Environment—and two community-based nonprofits, Brightline Defense and NICOS Chinese Health Coalition. 

"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. "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." 

Today marks the anniversary of the 2017 Labor Day heat wave that brought the record breaking 106-degree heat in parts of the City—the hottest recorded temperature in San Francisco history. San Francisco is also facing a forecasted heat wave over the coming week, with temperatures expected to reach the 80s with even hotter temperatures in the southeastern parts of San Francisco. 

As the city prepares for extreme heat, the San Francisco Department of Emergency Management is leading the city’s coordination, collaboration, and resource needs for this extreme heat situation.  

“Over the past five years San Francisco has experienced more extreme weather due to our changing climate. Labor Day Weekend 2017 was a warning to the leaders of our typically temperate city that we had to adapt how we plan and prepare for emergencies,” said Mary Ellen Carroll, Executive Director of the Department of Emergency Management. “As we prepare for our warmest months of the year in San Francisco, it is vital we consider those who may be especially vulnerable to heat, like older adults, infants, those with disabilities, and anyone we know who may have difficulty keeping cool during a heat wave in San Francisco.”  

As the City government prepares for extreme heat, San Francisco residents and visitors must know what to do to stay healthy and safe during heat waves, especially regarding the following:  

  • Heat impacts your body immediately within hours so prioritize keeping cool. Even a few hours in a cooler setting can prevent heat illness. If it feels too warm inside, go outside and find shade to avoid direct sunlight. Wear lightweight, light-colored clothing.  

  • For people visiting San Francisco beaches from other parts of the Bay Area to beat the heat, riptides and sneaker waves can make our beaches dangerous places to swim. We recommend avoiding the water, especially on crowded days. 

  • Look before you lock. Especially if you are traveling with young kids, seniors or people with disabilities, or pets. Heat deaths are preventable. Outside temperatures of 80 degrees can rise to 99 degrees inside a locked car in just 10 minutes & 123 degrees after an hour. 

  • Windows can be powerful natural air conditioners, but as temperatures rise and we open windows more than usual, this increases the risk of falls for young children. If possible, install safety gates on open windows, and always keep an eye on young children. 

  • Look out for one another. Check on friends, family, and neighbors that may be vulnerable to heat. Call 9-1-1 if you or some else is experiencing symptoms of heat illness or is having a medical emergency. 

For more information about how to be healthy and safe during a heat emergency visit To sign up for official city emergency alerts delivered by text message, text your zip code to 888-777.