 Hurricane Beryl is approaching the windward islands of the Caribbean as a Category 4 hurricane. Here's NPR's Rebecca Herscher. Category 4 storms have winds of 130 mph or more, which can rip the roof off many buildings. The storm gained strength very quickly. In less than two days, its maximum wind speed increased by about 75 mph. Rapid intensification is relatively common for major hurricanes, but it usually doesn't happen this early in the summer.