From Public Forecasts to Occupational Heat Safety Management: Evaluating the Effectiveness of the National Weather Service's Operational Heat Risk Forecasts.

Heat poses a major environmental risk to occupational safety, necessitating timely insights into associated risks to safeguard workers. In June 2022, the National Weather Service (NWS) initiated operational wet bulb globe temperature (WBGT) forecasts, offering valuable information for heat risk management. This study evaluates the effectiveness of NWS WBGT forecasts, aiming to identify potential areas of caution and improvements for their application for occupational safety management. To this end, the study examines 1.3 million hourly historical NWS WBGT forecast data, comparing it with observed data from 252 weather stations across the US during the summer of 2023. The results offer key insights, revealing that: (1) the accuracy of NWS WBGT forecasts is influenced more by the times of interest than by the forecast horizons; (2) NWS WBGT forecast accuracy varies across different climates in the US, with air temperature bias being the most influential factor in this inaccuracy; and (3) while NWS WBGT forecasts accurately identify the lowest heat risks (i.e. no heat risk), their performance decreases at higher risk levels, emphasizing the importance of careful interpretation in safety management. These insights offer guidance for more cautious interpretations of NWS WBGT forecasts and lay the foundation for future studies on leveraging operational weather forecasting services in effective heat mitigation strategies.