In this paper we study again the effect on mortality of the extreme Dutch winters and
summers of the nineteenth and twentieth centuries.We focus on those topics which already attracted the attention of medical doctors at the time: Were some age groups more vulnerable than others? Were there social classes that had to endure the effects of heat and cold more than other groups? Were there indeed short-term and longer-lasting effects of heat and cold? In contrast to the nineteenth-century studies, we combine
detailed mortality and temperature data with advanced time-series methods to shed new light on the effects that heat waves and cold spells had on mortality in the past. Questions such as these have only received limited attention by historians.