Every time a hurricane closes in on the US coast, there is a team of people ready.

They are taking in data on power outages, road closures, storm surges and flooding.

They have generators at the ready, trucks carrying supplies, and workers ready to come in at any moment to help fill any staffing shortages.

All to serve hamburgers and eggs to hungry diners at any of the 1950 Waffle Houses in storm-affected restaurants.

Waffle House restaurants are designed to open quickly after a natural disaster. (AAP)

And at the Federal Emergency Management Agency, officials are asking one question to determine how bad a natural disaster has been – is the Waffle House open?

FEMA has developed a term for it: The Waffle House Index.

The Waffle House Index

The term stemmed from former FEMA director Craig Fugate's observation in 2004.

"If you get there and the Waffle House is closed? That's really bad," he told the Wall Street Journal .

"That's where you go to work."

Waffle House has a reputation for staying open during natural disasters. (AP)

Waffle House is a chain of diners dotting the US south, serving steaks, hamburgers, eggs and waffles at all hours.

The restaurant is known for being open 24 hours a day, seven days a week. There's a legend that the keys to each Waffle House are buried in the cement footpath out front, because they are never needed. It's not true, but it might as well be.

"We don't close," Waffle House's public relations director Pat Warner told 9News.

But being centred around the southeast US, many Waffle House restaurants find themselves in the path of hurricanes, tornadoes and floods.

And Waffle House has made it company policy to stay open.

Why is Waffle House always open?

"It's part of our company culture to get back to normal as quickly as possible," Mr Warner said.

"We have a lot of resources we will send into an area to get the restaurant up and running."

There are nearly 2000 Waffle Houses in the United States. (AAP)

A storm manual guides employees through customised menus tailored to particular challenges.

"There's a no power menu," Mr Warner said.

"We have one we can go on with a water disruption.

"We look at our menus and walk through different scenarios.

"Our goal is to get to the full menu as quickly as possible."

Being the only restaurant open may seem like a lucrative proposition, but it's not about the bottom line for Waffle House.

"We will be busy, but when you factor in the resources that we're deploying, it's not a business decision," Mr Warner said.

"In big storms we may lose money because of the resources we put in place."

Customers at Waffle House are "used to us always being open", Mr Warner said.

"For us it's more about the people. If we're open the community feels that they're getting back to normal," he said.