2015), and several case studies suggest that alerts have helped prevent injuries and deaths ( Ebi et al. There is clear evidence that weather alerts are effective in triggering behavior change by organizations and individuals ( Liu et al. Alerts are intended to encourage protective behavior (e.g., evacuation, seeking shelter, avoiding driving, wearing appropriate clothing) for the public at large and for institutions and organizations that may play a role in preparing for or responding to a dangerous meteorological event. Weather alerts (including advisories, watches, and warnings) are important risk communication tools widely used by meteorological agencies to notify the public of the onset of dangerous conditions. Keywords: Extreme events Communications/decision making Emergency preparedness Geographic Information Systems (GIS) Health Societal impacts Our results suggest that the public may be receiving mixed signals about the severity of the heat hazard, with some hotter locations particularly underserved by heat risk messaging. Locations that issued heat alerts more frequently than would be expected based on climatology were primarily located along the Pacific coast those that issued heat alerts less frequently than expected were in southern Texas and southern Florida, the latter of which includes multiple cities with high rates of heat-attributable mortality. The 95th-percentile daily maximum heat index was the climatological indicator most strongly correlated with heat alert frequency across all WFOs ( r = 0.71). Regions with the highest frequency (approaching 25 heat alert days per year) included the southern Midwest and Great Plains, as well as the desert Southwest.

The median location experienced 2.3 heat alert days per year. Across 77% of the country, heat advisories were the primary product issued.

The type of heat alerts used and the frequency with which they were issued were highly variable. Heat alert frequency was correlated to climatological indicators derived from reanalysis data aggregated to Weather Forecast Office (WFO) polygons and to estimates of heat-attributable mortality for 134 metropolitan areas. We compiled and analyzed all excessive heat warnings and heat advisories (collectively, heat alerts) issued by the U.S. Public heat alerts are important risk communication tools, but there has been no systematic analysis of how frequently they are issued or how patterns in alert frequency relate to regional climatology or heat–health impacts.

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