The California Heat Assessment Tool

As California’s climate warms, residents increasingly endure extreme heat events that adversely impact public health. This exacerbates existing risks and will bring new challenges for different regions in the state, threatening the efficacy of traditional intervention strategies. Current thresholds for heat alerts are based on temperatures that exceed historical statistical thresholds, rather than temperatures that cause public health impacts. These ‘health-neutral’ thresholds may underestimate the health risks for the most sensitive populations. The new California Heat Assessment Tool (CHAT) is based on research that establishes local, health-based thresholds for extreme heat that help public officials, health professionals and residents understand what changing conditions mean for them. CHAT is part of California’s Fourth Climate Change Assessment, a state-mandated research program to assess climate change impacts in California, and was developed by Four Twenty Seven, Argos Analytics, the Public Health Institute and Habitat 7 with technical support from the California Department of Public Health.

Explore CHAT at cal-heat.org.  This online tool advances the understanding of what types of heat waves pose public health risks and examines how the frequency and severity of local heat waves are expected to change over time due to climate change.

Read a brief report, The California Heat Assessment Tool: Planning for the Health Impacts of Extreme Heat, that shares key findings from the research and summarizes the data analysis visualized in the tool.

Access the technical report detailing technical methodology and view other projects funded by the California Fourth Climate Change Assessment.

Access the users needs assessment for a detailed explanation of the literature review and interview process that defines the data gap the research team addressed.

Download the full press release.

Key Takeaways

  • Current climate change projections show that a typical California summer in 2100 may be 4-5° F warmer than today. Heat waves are also lasting longer, occurring later into the summer season and in areas less accustomed to heat waves.
  • Elderly or very young people, outdoor workers and individuals with preexisting health conditions or limited resources are most sensitive to the impacts of extreme heat and may be disproportionately affected. Some of these sensitive, or frontline, populations may experience adverse health impacts at temperatures 6-8° F lower than the general population.
  • Current thresholds for heat alerts are based on temperatures that exceed certain statistical thresholds, rather than temperatures that cause public health impacts. These health-neutral thresholds may underestimate the health risks for the most sensitive populations.
  • The online California Heat Assessment Tool (cal-heat.org) allows users to visualize projected changes in heat events that cause adverse health impacts, while also exploring data on social, health and environmental factors that contribute to heat vulnerability.