MIAMI (AP) - A minor change is coming to the five-category system describing hurricane strength.

The Saffir-Simpson Hurricane Wind Scale starts at Category 1 with top sustained winds at 74 mph. Categories 3 and above are considered "major."

The National Weather Service says an adjustment was necessary to smooth converting units of wind speed measurement for public advisories.

The change broadens the Category 4 wind speed range to 130-156 mph, instead of 131-155 mph. That shifts the Category 3 range to 111-129 mph, instead of 111-130 mph.

Category 5 hurricanes will have top winds of 157 mph or higher, instead of a threshold of 156 mph.

Categories 1 and 2 remain unchanged. No historical storm records will be altered.

The change takes effect May 15.