Governor Newsom expands access to life-saving CalHeatScore, a cutting-edge tool to keep Californians safe during extreme heat

CalHeatScore Forecast for Thursday, May 21

About CalHeatScore

In a hotter, drier world, connecting Californians with extreme weather information and resources has never been more important.

As part of a broader climate package in 2022, Governor Newsom signed Assembly Bill 2238 by Assemblymember Luz Rivas to codify the California Department of Insurance’s Climate Insurance Workgroup recommendation by requiring the state to develop a statewide extreme heat ranking system.

In 2025, California became the first state in the nation – and one of the only jurisdictions in the world – to launch a heat-ranking system.

CalHeatScore, developed by the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA), brings together ZIP-code level data to provide locally tailored heat scores. It translates complex weather and health data into clear guidance and integrates other important data sets, like locations for the nearest cooling centers. CalHeatScore also provides local data on groups susceptible to extreme heat, such as older adults and children, to support community planning efforts and provides tips for staying safe, such as how to recognize signs of heat illness.  

The API is part of continuous efforts to develop, improve and broaden options for using CalHeatScore and keep Californians informed about extreme heat in their communities.

Dangers of Extreme Heat

Extreme heat is the leading cause of weather-related deaths in the nation, claiming more lives annually than any other climate threat, including fires and floods. In 2024, California communities experienced the hottest summer on record in 130 years. According to a report from the Department of Insurance, from 2013 to 2022, seven extreme heat events resulted in nearly 460 deaths, over 5,000 hospitalizations and about 344 adverse birth outcomes.