Towards an early warning system for heat events

Severe and sustained episodes of hot weather during the summer season are associated with marked short-term increases in morbidity and mortality in the United States and Europe. The death toll in an unprepared region can be substantial, as was evidenced in the 2003 heat event in Western Europe. There is growing interest in developing early warning systems to advise the public when weather conditions pose risks to health. These systems link meteorological forecasts of dangerous weather with public health actions. The principal components of an early warning system include identification and forecasting of the event (including consistent, standardised weather criteria for when warnings are activated and deactivated), prediction of possible health outcomes that could occur, an effective and timely response plan that targets high-risk populations, and an ongoing evaluation and revision of the system and its components. A particular challenge is the development of effective communication of the behavioural changes needed to prevent adverse health impacts.