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There are a few ways to gauge the expected severity of a hurricane, but one of the more unusual is by the Waffle House index. If Waffle House locations in the path of a hurricane are open, that’s a sign there is limited damage from the storm. If locations are closed — which is the case for some in Florida due to Hurricane Idalia — then conditions are unsafe.

The Waffle House index uses a green, yellow and red rating to measure how bad storms are: green means the full menu is being served and there is little storm damage; yellow means there is a limited menu because they are likely using a generator for power or they are low on supplies; red means the restaurant is closed because the storm is severe. 

As of midday Wednesday, 15 Waffle House locations were without power – but some were in the yellow zone of the index, because they were open and operating with generators, a representative for the chain told CBS News via email. At least five locations were in the red zone of the index, because they were in the direct path of Idalia after it made landfall. Two others in St. Petersburg were closed due to storm surge.

Hurricane Idalia, which made landfall Wednesday on Florida’s Gulf Coast, brought “catastrophic” storm surge and “damaging” winds to the area, the National Hurricane Center said. It was briefly a Category 4 storm before weakening to a Category 3.

Many of the 1,600 Waffle House locations are in hurricane-prone areas on the East and Gulf Coasts. Waffle House strives to be open when people are desperate – and the chain has proven to be reliable after devastating hurricanes. 

“I hadn’t had a hot meal in two days, and I knew they’d be open,” Waffle House customer Nicole Gainey told the Wall Street Journal after Hurricane Irene devastated North Carolina in 2017. Despite the storm knocking out power, a local Waffle House in Weldon stayed open – a beacon of hope for people like Gainey.