Waffle House has closed all its restaurants in Escambia and Santa Rosa counties as Hurricane Isaias approaches Florida.

The chain, famous for staying open around the clock, shut its doors at 10 a.m. on Friday. Stores will reopen when conditions are safe.

Locals take the closures seriously. The Waffle House Index is an informal disaster metric used by FEMA. It measures storm severity by whether the restaurants stay open.

The Pensacola area locations were set to ‘threatened’ status, meaning they are at severe risk of closure.

Isaias is expected to make landfall Friday evening near the Florida Panhandle as a major hurricane, with up to 9 feet of storm surge.

When Waffle House closes, residents know a storm is serious. The closures underscore how closely the region is watching this storm.

The index has three levels: green for open, yellow for limited menu, red for closed. Pensacola’s closures put the area firmly in red territory.

FEMA’s former chief once said the index was the most honest storm gauge he had. If Waffle House is closed, the storm is bad.