This paper provides coherent evidence on what Europe might expect in the case of a worst-case heat and drought event. The record-breaking heat in 1540 was an analogous case to the 2003 event, albeit more intense, longer lasting and affecting a larger area—extending from France to Poland and from Italy to Germany, also including Spain and Morocco. Both in Switzerland and in Poland, precipitation in spring, summer, and autumn was below twentieth century averages. Discharge deficits of ninety percent were assessed for major rivers. Due to the extreme soil dessication, maximum temperatures in early August probably rose above 40ºC. By then, forest and settlement fires were ravaging throughout continental Europe. Premodern societies were surprisingly resilient to extreme conditions, notwithstanding the widespread dysentery, cattle mortality, and forest fires. The majority of the impact of a 1540-like event on present societies would be caused by the resulting severe water shortage and its cascading across interlinked systems. In particular, fossil and nuclear energy production, which depend on a sufficient amount of cooling water, would be significantly affected. Such a shortage might entail longer-lasting power blackouts with disruptive impacts on societies and economies.