http://www.newsweek.com/hurricane-ian-category-4-5-florida-categories-explained-1747207

Hurricane Ian is set to batter Florida with sustained winds of 155 miles per hour on Wednesday as it makes its way towards land, bringing with it life-threatening winds and flooding.

As of noon ET, the hurricane had developed maximum sustained wind speeds of 155 miles per hour, making it a Category 4 storm on the verge of a Category 5—the most severe type. At that time, several storm surge warnings were in effect, meaning there is a danger of catastrophic flooding from rising water moving inland from the coastline.