The chain, whose restaurants are open 24 hours a day, 365 days a year, is famous for staying open during many natural disasters. When it closes, that suggests an event was especially bad and likely to have devastating effects on the economy.
Because of this, FEMA internally uses an unofficial “Waffle House Index” to track potentially dangerous events.
“If a Waffle House store is open and offering a full menu, the index is green,” a 2011 article in the magazine EHS Today says. “If it is open but serving from a limited menu, it’s yellow. When the location has been forced to close, the index is red.”