It's a shocking tweet for anyone who knows a bit about natural disasters -- or enjoys waffles and pancakes at 2 a.m.

Waffle House doesn't close. Ever. Unless there's a really bad emergency situation.

So a tweet from the Waffle House PR account Monday has an ominous feel to it:

FEMA actually uses what's called The Waffle House Index to help measure a storm's impact.

If a Waffle House is open and serving a full menu after a hurricane, FEMA knows things are going well and the index is green.

If the 24-hour diner is only serving a limited menu, it means there may be supply or power issues in the area. The index is yellow.

But if a Waffle House is closed -- the index is red.

Former FEMA Administrator Craig Fugate began using the Waffle House Index during his time in charge of Florida's emergency response during disasters like the 2004 Florida hurricanes. Fugate said the Waffle House Index is a good indicator of how well a community can bounce back after a storm.

Waffle House tweeted Tuesday that locations were open in the following places:

Be aware -- prices may be different, and the locations may have limited menus.