In a time of natural disaster, the federal government uses a simple gauge to determine the toll Mother Nature has taken on a local area.

It's called the Waffle House Index, or test, which uses the operating conditions of the resilient Southern restaurants as a barometer for how well an area will recover from a hurricane, tornado or other hazard.

"The Waffle House test just doesn't tell us how quickly a business might rebound — it also tells how the larger community is faring," said a FEMA blog post from 2011, when Craig Fugate was administrator under former president Obama. "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."

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Fugate said the system "came out of the '04 hurricanes," when he was Florida's emergency management director. Here's how Fugate described the test on a 2016 episode of NPR's comedy podcast Wait Wait... Don't Tell Me:

"They are open most of the time. And that was the index. If a Waffle House is closed because there's a disaster, it's bad. We call it red. If they're open but have a limited menu, that's yellow," he said. "If they're green, we're good, keep going. You haven't found the bad stuff yet."

If the test is to be believed, Hurricane Irma promises to pack a bigger wallop than Hurricane Harvey. Pat Warner, spokesman for Waffle House, said 40 Waffle Houses around Houston were affected by Harvey. The company expects about 250 restaurants to feel the impact from Irma.

Waffle House holds the FEMA test as a point of pride. The company's goal is to reopen its stores as quickly as possible after a storm passes. The company claims getting back to business restores a sense of normalcy in affected areas. Before a storm hits, the store brings in extra supplies and has managers on standby to help. Most of the 1,900 Waffle Houses are located in the southeast United States, meaning the company is used to battling big storms.

Fugate stepped down in January and was replaced by Brock Long, but the Waffle House Index remains. In an email, a FEMA spokesperson stressed the index is an "unofficial metric."

Follow Sean Rossman on Twitter: @SeanRossman