September 15, 2018 GMT

As Hurricane Florence nears, FEMA will be keeping a close eye on the Waffle House — the fast-food restaurant chain known for staying open 24 hours a day every day of the year.

The agency coined the term “Waffle House Index” during the 2004 hurricane season to measure the effect of a natural disaster on an area. If the eatery shutters or limits menu items during or after a hazard — they know the community took a major hit.

The index has three color-coded levels: Green means everything is fine, at least in the Waffle House; yellow is when the restaurant serves a limited menu, meaning the area lost power or they’re running low on supplies; and red is if it’s closed, showing the area has been hit hard.

“The Waffle House test just doesn’t tell us how quickly a business might rebound — it also tells how the larger community is faring,” FEMA said in a 2011 blog post. “The sooner restaurants, grocery and corner stores, or banks can re-open, the sooner local economies will start generating revenue again — signaling a strong recovery for that community.”

The chain posted a photo Wednesday of corporate employees monitoring the storm’s path as they decided if any locations would close. “The Waffle House Storm Center is activated and monitoring Florence.

Plan ahead and be safe,” they tweeted. At least one location in Myrtle Beach, South Carolina, had shut its doors by Wednesday night.