Hurricane Dorian: Six things to know about Category 4 hurricanes.

Hurricane Dorian is now expected to strengthen into a dangerous Category 4 storm before making landfall along Florida’s east coast early next week.

Dorian was moving northwest through the Atlantic Ocean after pummeling Puerto Rico with rain. It was a Category 1 storm on Thursday afternoon, packing 85 mph sustained winds. Forecasters think it will intensify into a Category 4 storm as it crosses warm waters on its approach to Florida.

Here are some quick facts about Category 4 storms:

• Since 1924, more than 110 storms that formed in the Atlantic Basin, including the Caribbean and Gulf of Mexico, have strengthened into Category 4 hurricanes. Thirty-four went on to become Category 5s for at least a few hours, including last year’s Hurricane Michael. Most Category 4s occur in September, but monster storms often form in late August and early October, too.

• It’s highly unusual for a hurricane to make landfall as a Category 4 storm in the United States. Only 14 have done it since 1924. (The number rises to 18 if you include the four storms that rolled ashore as Category 5s). Seven storms made landfall in Florida packing Category 4 winds. Three more came ashore in our state as Category 5 storms: the 1935 Labor Day hurricane, Hurricane Andrew in 1992, and Hurricane Michael last year.

• Hurricane Charley in 2004 was one of the most destructive Category 4 storms to hit Florida. It was a fast-moving buzz saw that packed 150 mph winds. It demolished parts of Port Charlotte and Punta Gorda and carried enough of a wallop inland to create considerable damage in the Orlando area, including Winter Park. The storm was blamed for 10 deaths and more than $15 billion in damage. In 2017, Hurricane Irma roared ashore in the Florida Keys as a Category 4 storm and them marched up the state, forcing an estimated 6.5 million people to evacuate.

• Category 4 storms include sustained winds of 130–156 mph, measured 33 feet above the ground. Winds that powerful can easily destroy mobile homes, snap trees and chew the roofs off even the most well-built homes. In 2004, Tampa Bay Times reporters observed Hurricane Charley strip the paint off of a car.

• Don’t think of a Category 4 storm packing 150 mph winds as being twice as strong as a Category 1 with 75 mph winds. The Cat 4 is much, much more powerful. Why? Wind power is exponential. Put another way: The winds from a strong Category 4 storm (156 mph) have the potential to create twice as much damage as a weak Category 4 storm (130 mph).

• Category 4 storms can also create 15 to 20 feet of storm surge. Power can be knocked out for days, and in some cases, weeks or even months. Hurricane experts routinely describe the damage wrought by Cat 4s as "catastrophic."

* This article is an update of a similar list complied by the Times in 2016.

Sources: National Hurricane Center, National Weather Service, Massachusetts Institute of Technology.