Meet the 2021 Campaign Cities

San Francisco, California

Year: 2021

Campaign Lead Organization(s): San Francisco Department of Public Health

Get Involved:

Matt Wolff |


More hot days by the end of the century compared to the beginning (US CRT Climate Explorer)


Population that does not speak English "very well" compared to 8.4% national average. (2019 ACS - US Census)


Population living in poverty, compared to 12.5% national average. (2019 ACS - US Census)


Population living alone, compared to 15% national average. (2019 ACS - US Census)


In San Francisco, heat waves are getting hotter, lasting longer, and with higher nighttime temperatures. These heat waves are having significant, cascading and compounding impacts on public health. 

On the Friday of the 2017 Labor Day weekend, temperatures in San Francisco hit 106 degrees, the highest temperate ever recorded in the City and 37 degrees warmer than the average temperature for that day. The heat wave continued into Saturday, making it only the third time in recorded history that San Francisco’s temperatures hit triple digits two days in a row. 

There were over 1,300 9-1-1 calls on Friday September 1st, more than double the number of calls the previous Friday and there was a 17% increase in Emergency Department visits. These health impacts are consistent with the literature: a California Department of Public Health epidemiological study of a 2006 statewide heatwave found that Emergency Department visits increased more in California Central Coast communities (like San Francisco) than anywhere else in the state. 

San Francisco is particularly vulnerable to the health impacts of extreme heat events because, among other things,

  1. San Francisco is an urban heat island with tree coverage, park access, and concrete distributed unevenly throughout the city,
  2. Our bodies aren’t physically used to extreme temperatures, and 
  3. As a temperate city with housing and infrastructure built for a coastal climate, our built environment is not weatherized to withstand extreme temperatures. Most of the health impacts of extreme heat in San Francisco happen indoors. San Francisco has limited cooling capacity, and this cooling capacity is not equitably distributed. 

This Urban Heat Island mapping campaign with help San Francisco target interventions towards the neighborhoods and communities that carry the greatest health burden of extreme heat by identifying which communities are particularly exposed to the hazard.  

Lead Organization(s)

San Francisco Department of Public Health

Partner Organizations

  • San Francisco Department of Environment
  • Brightline Defense Project 
  • Neighborhood Empowerment Network
  • NICOS Chinese Health Coalition

Campaign Goals / Anticipated Outcomes

  • Understand the disproportionate impacts of urban heat islands within San Francisco.
  • Develop capacity to partner with community organization to target resources at the communities that carry the heaviest health burden.
  • Cultivate partnerships that will enhance our insight and resources for community outreach during extreme heat events.
  • Minimize the number of hospitalizations and emergency room visits during extreme heat events.



NIHHIS is made possible by our participating agencies.













NIHHIS Headquarters

Address: 1315 East-West Hwy, Suite 1100
Silver Spring, MD 20910

About Us

NIHHIS is an integrated information system that builds understanding of the problem of extreme heat, defines demand for climate services that enhance societal resilience, develops science-based products and services from a sustained climate science research program, and improves capacity, communication, and societal understanding of the problem in order to reduce morbidity and mortality due to extreme heat.  NIHHIS is a jointly developed system by the Centers for Disease Control and Prevention (CDC) and the National Oceanic and Atmospheric Administration.

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