A man cools off in a fountain in New York’s Washington Square Park this summer. Death from all causes doubled during a heat wave in New York City in August 1975, with heart attacks and strokes accounting for a majority of the excess deaths.

A man cools off in a fountain in New York’s Washington Square Park this summer. Death from all causes doubled during a heat wave in New York City in August 1975, with heart attacks and strokes accounting for a majority of the excess deaths.