European heatwave of 2003
An anticyclone parked over western Europe for weeks; France recorded over 14,000 excess deaths in two weeks, most of them elderly, and electricity demand spiked as the grid strained.
More than 70,000 excess deaths across the continent; hospitals and crematoria were overwhelmed.
Spurred national heat plans and early-warning systems across Europe, making heat a public-health category.
The clearest precedent for how a record summer becomes a mass-death event and an infrastructure crisis.
