ON July 22, planet Earth achieved a terrifying milestone: Global temperatures reached their highest level in recorded history, breaking a record set just one day before. This year is expected to be the hottest in centuries. Heat waves are hotter, longer and more frequent than they were in the 1960s.
By now, most of us understand that extreme heat is bad for our health, making our hearts, lungs, kidneys and other organs work much harder. But too often we overlook the quieter, less obvious toll heat takes on another vital organ: our brain.
