California Heat Assessment Tool (CHAT)

The California Heat Assessment Tool (CHAT) was developed to help state and local public health officials understand how heat vulnerability will change with increasing temperatures due to climate change. The tool helps users identify heat vulnerable areas based upon changes in high heat days under different climate scenarios and social, health and environmental vulnerability factors. The study defines "Heat Health Events" (HHEs) as heat events that cause negative public health impacts - and the study found that vulnerable groups may be more sensitive to high-heat days by as much as 6 to 8 degrees Fahrenheit as compared to the general population. The tool helps users determine how climate change will affect the severity, duration, and shifts in timing of HHEs under different emissions scenarios. 

Users can map projected changes in HHEs and assess heat vulnerability using a range of different indicators including:

  • social vulnerability (e.g., education level, poverty, access to vehicles, linguistic isolation, outdoor workers)
  • health factors (e.g., rates of asthma, child birth weights, and rates of cardiovascular disease), and
  • environmental factors (e.g., particulate matter concentrations, ozone exceedances, percent impervious surfaces, percent lacking tree canopy, urban heat islands).  

A resource page allows users to download data and access trainings and a technical summary of the findings from the research. This page also provides information about groups that can provide technical assistance on heat vulnerability and health - and offers resources describing solutions for reducing urban islands, protecting seniors, preventing heat illness, and increasing tree canopy.

CHAT was developed by Four Twenty Seven, Inc. in partnership with Argos Analytics, Habitat Seven, and the Public Health Institute. The work was funded by the California Natural Resources Agency as part of development of the state's Fourth Climate Change Assessment.


Publication Date: 2019

Related Organizations:

  • California Natural Resources Agency
  • Four Twenty Seven


Resource Category:

Resource Types:

  • Assessment
  • Websites

States Affected:


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