Hurricane Irma claimed the lives of multiple people across the Caribbean as the powerful Category 5 storm's 185-mph winds swept past Puerto Rico toward the Dominican Republic and Haiti. It could be on a collision course with South Florida over the weekend.

If Irma hits the U.S. as a Category 5 storm, it would be just the fourth hurricane of that strength to do so in recorded history. The storm was downgraded to a Category 4 early Friday morning with sustained winds dropping to 155 mph.

Governors of three Southeast states already have declared states of emergency, and mandatory evacuations took place in the Florida Keys and were set to begin Thursday in the Miami area. Here is what we know now:

Irma is a historically powerful storm

Irma rolled into the region as the most powerful Atlantic Ocean hurricane ever recorded above the Caribbean and east of the Gulf of Mexico. The National Weather Service says Irma will remain a Category 4 or 5 hurricane over the next couple of days, with hurricane-force winds extending up to 50 miles from the center and tropical-storm-force winds extending 175 miles. Irma is so strong it's even showing up on equipment designed to measure earthquakes. After Irma struck Barbuda, its prime minister called the island "barely habitable" and St. Martin, an island split between French and Dutch control, saw extensive damage and was almost completely destroyed in places.

It's coming our way

Hurricane and tropical storm conditions descended on the Dominican Republic and Haiti Thursday and could move into the central Bahamas and Cuba by Friday, the weather service says. The storm was moving at about 17 mph. In Florida, the Coast Guard shifted into "Hurricane Condition Whiskey" in the Port of Key West. That means sustained, gale-force winds from a hurricane-force storm are predicted by Saturday morning. The full brunt is forecast to arrive sometime Sunday, although exactly when and where remain difficult to determine. "Do not sit and wait for this storm to come. Remember, we can rebuild your home — not your life," Gov. Rick Scott said.

Damage could be catastrophic

Florida has seen Category 5 hurricanes before. Hurricane Andrew roared into South Florida 25 years ago, a fast-moving storm that flattened neighborhoods, tossed cars and trucks around like Matchbox toys, and left millions without power. The storm destroyed more than 25,000 homes and damaged 100,000 others. An Andrew-like storm hitting downtown Miami could cause $300 billion in damage, according to one insurance underwriter. The National Hurricane Center reports that when a Category 5 hurricane hits land, "a high percentage of framed homes will be destroyed," adding power could be lost in some areas for "weeks and possibly months."

Preparations underway in earnest

Scott, Georgia Gov. Nathan Deal and South Carolina Gov. Henry McMaster declared states of emergency in advance of the storm. Monroe County, home of the Florida Keys, declared a state of local emergency due to a “threat of danger to the populace" and ordered everyone to evacuate. Tourists were ordered off the islands Wednesday morning, and residents later in the day. The City of Miami Beach distributed sandbags.

Pet vets: Don't forget Fido and Fluffy

The American Veterinary Medical Association is reminding pet owners developing disaster plans to include pet evacuation kits. The list is extensive. Important components include 3-7 days worth of food, a two-week supply of medicine, 7 days of water, a dish and water bowl, flea and tick prevention, ownership documents and some "comfort" toys. Veterinarian Michael Topper, president of the AVMA, says to take a picture with your pet so that you can prove ownership if you get separated. "The critical things are food, medication and identification," Topper said. And don't forget the pet first-aid kit of antibiotic ointment, bandages, saline and related equipment.

Strongest storm to hit U.S. was in 1935

The strongest storm ever to make landfall in the U.S. hit on Sept. 2, 1935. Hurricanes were not officially named back then, but this one became known as the Florida Keys or Labor Day hurricane because of where and when it hit. The hurricane slammed across South Florida with sustained winds of 185 mph, killing 423 people. Among the dead: 259 World War I veterans living in camps while building the highway to Key West. Awful as that storm was, perhaps the most horrific storm came 35 years earlier, flattening Galveston, Texas, and killing an estimated 6,000 to 8,000 people.

Between Andrew and 'Labor Day': Camille

Besides Andrew and the so-called "Labor Day" hurricanes, one other Category 5 storm blasted into the U.S. — Camille in 1969. Camille struck the Gulf Coast on Aug. 18 of that year with sustained winds estimated at 175 mph and gusts of 200 mph. Storm surge — the wall of ocean water that comes ashore with the hurricane — brought devastation to coastal Mississippi. Torrential rain from Camille led to additional flooding and deaths well inland as the storm crossed Virginia's Appalachian Mountains. In all, Camille killed 259.


Contributing: Alan Gomez and Doyle Rice