President Trump said he wasn't aware "Category 5" hurricanes existed until Hurricane Irma.

At the White House Historical Association dinner Thursday, Trump discussed his trip to Florida, which is facing massive power outages and is recovering from the destruction of Irma, which had been a Category 5 hurricane.

"I never even knew a Category 5 existed," Trump said, according to a press pool report.

Hurricanes are graded according to the Saffir-Simpson Hurricane Wind Scale, which the National Hurricane Center uses, on a 1-to-5 rating scale based on a hurricane's sustained wind speed. Category 5 is the strongest, boasting winds of 157 mph or higher.

Irma was a Category 4 storm by the time it made landfall in Florida over the weekend.

Trump lauded the first responders who have been working in Florida by saying they did an "A-plus job."

Trump announced earlier in the day Thursday he would be visiting Puerto Rico and the Virgin Islands in the coming weeks as they too recover from Irma.