CalHeatScore, a new online mapping tool from California’s Office of Environmental Health Hazard Assessment (OEHHA), is giving communities a clearer way to understand heat danger, similar to what the Saffir–Simpson scale did for hurricanes. The platform ranks extreme heat health risk for every California ZIP code on a simple 0–4 scale, delivers warnings days in advance, and lets users overlay nearby public cooling centers with addresses, hours, and contact information.
The team presented the work at AGU’s Annual Meeting 2025 in New Orleans on Dec. 16, sharing how the model links heat forecasts to real health outcomes to support decision-making by meteorologists, emergency managers, agencies, and the public. The presentation, led by C-Solution’s collaborator Dr. John Molitor, also highlighted why a shared, hyperlocal warning system matters in a state where heat risk can vary sharply by neighborhood and community conditions. The tool’s urgency was underscored by a 10-day September 2022 heat wave that broke 1,500 temperature records and was linked to 395 excess deaths, helping spur momentum for a statewide warning system.
Officially called the California Communities Extreme Heat Scoring System, CalHeatScore launched in December 2024 to help prevent future heat deaths through streamlined, site-specific warnings paired with targeted public health guidance. To build the model, C-Solution’s research and project collaborators combined temperature data with emergency room visit data (2008–2018) for diagnoses that rise with heat and incorporated socioeconomic indicators to reflect how different communities experience the same temperatures. The system relies on spatial, multilevel modeling, while still delivering a simple, seven-day risk forecast. Dr. David Eisenman, the project principal investigator and co-director of C-Solutions, called the blend of health outcomes, temperature, and demographic data “a really unique approach,” and noted interest in adapting the model for other jurisdictions. If you’re interested in partnering with C-Solutions to develop a heat warning system for your region, contact us at [email protected]
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