People are keeping a close eye on Waffle House as Hurricane Florence churns toward the East Coast - and there's a weird reason why

AP

Waffle House is open 24 hours a day, 365 days a year.

• Waffle House is famously known for staying open during natural disasters. 
• The chain's policy has provided an unofficial way for the Federal Emergency Management Agency to track the severity of a natural disaster. If a Waffle House closes, it suggests the event was bad enough to potentially have devastating effects on the economy. The reverse is true if it stays open.
• Waffle House has not yet confirmed whether it will be closing restaurants during Hurricane Florence. 

The Federal Emergency Management Agency has an unusual way to track the severity of a natural disaster, and it involves Waffle House restaurants. 

The 24-hour, 365 days-a-year chain is famous for staying open during natural disasters, so when it closes, it suggests that the event was especially bad and likely to have devastating effects on the economy. The reverse is true if it stays open.

Because of this, FEMA uses an unofficial "Waffle House Index" to track potentially dangerous events internally. 

If a Waffle House restaurant is open and offering a full menu, the index is green. 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. 

"The Waffle House test doesn't just tell us how quickly a business might rebound - it also tells us how the larger community is faring. The sooner restaurants, grocery and corner stores, or banks can re-open, the sooner local economies will start generating revenue again - signaling a stronger recovery for that community," FEMA wrote in a blog post in 2011, when Craig Fugate was administrator under President Barack Obama.

Waffle House announced on Twitter that its "Storm Center" is in the process of monitoring Hurricane Florence, which is expected to hit the coast between North Carolina and South Carolina late Thursday evening or early Friday morning.

The company is advising people to look out for updates on Twitter.

"Since it is a pretty active storm, just stay tuned to our @wafflehousenews Twitter, official announcements will be made there," it tweeted on Wednesday morning. 

A spokesperson for the brand did not immediately respond to Business Insider's request for comment. However, a customer-service assistant said that it has not yet confirmed whether stores will close.

Waffle House has 2,100 restaurants across 25 states, most of which are located in the South. It closed locations during Hurricanes Matthew and Harvey. 

Hurricane Florence has been designated a Category 4 hurricane with maximum sustained winds of up to 130 mph. This would be the first hurricane of this strength to hit North Carolina since Hurricane Hugo in 1989.