On This Day in 2012: The Mid-Atlantic Derecho

On this day in 2012, a wall of storms known as a derecho raced from Indiana to the Atlantic coast in a single afternoon, with winds over eighty miles an hour along a seven hundred mile path. It arrived with little warning and left power out for more than four million people across a dozen states.

The timing made it worse. The storm hit during a punishing heat wave, so families lost air conditioning just as temperatures climbed past a hundred degrees, and the outages stretched on for a week or more in some areas. The heat, not the wind, caused most of the deaths that followed.

The lesson is that a summer extended power outage is a heat emergency. A plan to stay cool without electricity, plenty of stored water, and a way to keep phones and medical devices charged are what carry a household through the days after the storm passes.