California launches heat wave risk tool CalHeatScore ahead of summer highs

REDLANDS, Calif. — As triple-digit temperatures loom across California, state officials have launched a new online tool aimed at protecting residents from the growing threat of extreme heat.

CalHeatScore, developed by the Office of Environmental Health Hazard Assessment (OEHHA), provides localized heat severity forecasts by ZIP code and connects users to resources such as nearby cooling centers, safety tips, and guidance tailored to vulnerable groups like older adults, children, and outdoor workers. The new tool was announced in a press released by the Office of Environmental Health Hazard Assessment on May 29, 2025.

“Every single preventable death is one too many,” said Yana Garcia, California’s Secretary for Environmental Protection. “This groundbreaking tool will help Californians plan and respond so they can stay safe when a heat wave is about to strike.”

Extreme heat is the state’s deadliest climate-related hazard, with recent data showing hundreds of deaths, thousands of hospitalizations, and significant economic losses in the past decade. According to the Department of Insurance, seven major heat events from 2013 to 2022 led to nearly 460 deaths and $7.7 billion in damages from lost wages, agricultural impacts, and power outages.

OEHHA officials say CalHeatScore responds to those risks by accounting for both temperature and local conditions. A reading of 95°F in Redlands, for example, may have very different health implications than the same temperature in a coastal community.

“CalHeatScore’s localized approach ensures that every Californian has the tools and knowledge to protect themselves and their loved ones during dangerous heat events,” said Dr. David Edwards, OEHHA’s chief deputy director.

The tool is part of a larger state initiative to reduce the public health impacts of climate change. It was developed in response to Assembly Bill 2238, authored by Assemblymember Luz Rivas and signed into law in 2022. OEHHA partnered with agencies including Cal OES, the Department of Public Health, and UCLA’s Center for Healthy Climate Solutions to build the tool using the best available science.

The first of six public webinars about CalHeatScore will be held Thursday, June 12, from noon to 1 p.m. on Zoom. It will provide an overview of the tool, guidance on how to use it, and ways to share feedback.  

Register for the Zoom.

To learn more about CalHeatScore, visit calheatscore.calepa.ca.gov.