Mapping heat alert systems across Europe

High temperature extremes significantly threaten public health, prompting many countries to implement heat early warning systems (HEWSs). Many European countries adopted a HEWS after the 2003 heatwave, taking into account specific regional needs and country-specific characteristics. While some smaller countries issue country-wide alerts, others deploy regional or city-specific warnings. Moreover, certain countries have alert criteria tailored individually for different regions, reflecting local climatic conditions, urban heat island effects, and variations in population vulnerability.

The existing research mostly focuses on the HEWS or Heat-Health Action Plans (HHAPs) as a whole. So far, a limited number of studies has analysed the actual data of issued heat alerts – out of these studies, virtually all focus on a single country. We collected records of heat alerts issued in the past from  16 European countries to thoroughly investigate the utility of European HEWS, and we present an inter-country comparison highlighting the unique characteristics of the applied HEWSs. The countries included in our study are Belgium, Cyprus, Denmark, Finland, France, Germany, Hungary, Ireland, Netherlands, Poland, Portugal, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Our objective is to introduce the data in a novel way by incorporating ERA5-Land reanalysis data to characterize the meteorological conditions on days when heat alerts were issued, and to assess their consistency. The aim is to provide insights into the correlations between heat warnings and actual weather patterns, thereby enhancing our understanding of how these systems can be optimized for better public health outcomes.

This study serves as a foundational step for a broader, more detailed analysis aimed at evaluating the effectiveness of heat alerts in protecting public health. Future research will adopt a counterfactual approach, comparing observed outcomes such as mortality on heat alert days with outcomes on climatically comparable days that could be eligible for the same heat warning, thus providing a clearer picture of the impact and efficiency of HEWSs.