NOAA/NWS HeatRisk v2: An Impact-Based Approach to Communicating Heat

Every year, on the order of 1,000 people die in the US due to heat-related illness (CDC, NOAA), making heat far more deadly than tornadoes, lightning, and floods. Research suggests heat-related illness is 10-20x mortality rates. Cooling costs, lost productivity, health care costs, and more add up to billions of dollars of impacts to the US economy. The NOAA/National Weather Service (NWS) issues heat watches, warnings, and advisories (W/W/A) to highlight impactful heat across the US, though they are often based on single thresholds for broad areas and do not account for small scale climatological differences. Heat-health research tells us no single threshold exists for triggering heat alerts.

Initially developed in 2013, the NOAA/NWS HeatRisk prototype provides a new and grounded method to alert the public to the dangers of heat. HeatRisk is a multi-tiered framework that applies a consistent approach, incorporating high-resolution climatology, CDC county-level heat-health data, and peer-reviewed heat science results, into a numeric and color-based system. HeatRisk leverages existing NOAA/NWS temperature forecasts to provide a seamless heat service through the entire seven-day forecast period. With multiple categories, HeatRisk provides information for those who are more vulnerable or with greater exposure to heat. It is used across the NWS Western Region to make heat watch/warning decisions. In 2022, HeatRisk was updated to version 2, which included scientific updates through collaboration with CDC, use of new NOAA/NCEI normals, and methods to better capture extreme events in modestly cool climates (e.g. Pacific Northwest heat event of 2021) and in the more humid east.

This presentation will discuss how HeatRisk is created and how it is used to message the range of heat impacts that occur within our communities. Impact-based verification will also be discussed, further demonstrating the utility of HeatRisk.