Waffle House Index: How it measures the severity of a hurricane

Hurricane Ian making landfall in Florida

Hurricane Ian’s most damaging winds began hitting Florida’s southwest coast Wednesday, lashing the state with heavy rain and pushing a devastating storm surge after strengthening to the threshold of the most dangerous Category 5 status.

ORLANDO, Fla. - As Hurricane Ian threatens to make landfall in Florida, the Waffle House Index is on standby ready to be used to determine the storm's impact on the state.

But what is the Waffle House Index?

FEMA has been using the Waffle House Indicator to measure the severity of a storm. It started in 2004 after Hurricane Charley, assigning color codes to measure the impact a natural disaster has on an area. The measure is based on the reputation of Waffle House for staying open during extreme weather and for reopening quickly after severe weather events such as tornadoes or hurricanes.

It goes like this:

GREEN: full menu- restaurant has power and damage is limited or no damage at all
YELLOW: limited menu- no power or only power from a generator, or food supplies may be low
RED: the restaurant is closed- indicating severe damage or severe flooding

"Waffle House became almost like a rough guidepost," former FEMA director Craig Fugate, the creator of the index, told FOX Business. "If it was open and had a full menu we probably weren't in the worst-hit areas yet."

Waffle House in Kissimmee, Florida. (Photo by John Greim/LightRocket via Getty Images)

"We actually have a storm playbook that every restaurant has. We revise it each year as needed. And it tells the management team what to do in the event of an emergency," said Njeri Boss, Vice President of Public Relations for Waffle House.

The restaurants have menus for the times they are without water, electricity, and even gas. The menus are limited and do not offer all of the options. This combination means the Waffle House Index rarely reaches the red level.

If a Waffle House closes before a storm, it is a sign that they expect extremely severe weather and that people in the area should also evacuate.

Waffle House has over 2,000 locations across the U.S. with more than 100 in Florida.

FOX Weather contributed to this report.