With Hurricane Irma bearing down on Florida and surrounding states, the mention of a Category 6 rating has been heard in the media. According to this there is no such rating.

With winds of 185 mph, Hurricane Irma is beating a path towards the United States mainland dropping it right in the middle of the Category 5 rating. These ratings are based on the Saffir-Simpson scale, first developed in 1971 by Herbert Saffir and Robert Simpson, a civil engineer and meteorologist, respectively.

The Saffir-Simpson scale is based on windspeed, using the maximum speed of sustained winds to organize hurricanes into the five established categories:

Category 1: Very dangerous winds will produce some damage. 74-95 mph winds.
Category 2: Extremely dangerous winds will cause extensive damage. 96-110 mph winds.
Category 3: Devastating damage will occur. 111-129 mph winds.
Category 4: Catastrophic damage will occur. 130-156 mph winds.
Category 5: Catastrophic damage will occur on a large scale. 157 mph or higher winds.

Since there is no Category 6 rating based on the Saffir-Simpson scale, it is pointless to call it such. Scientists and meterologists have been using the term loosely but according to the originals raings of the hurricane levels, this rating is false.

Is it be possible that a new rating should be added? Probably not since the Category 5 rating is catastrophic damage that will occur on a large scale. There's not really anything worse than that.