(CNN) -- The first Atlantic hurricane of 2011 strengthened to a Category 2 late Monday as it stormed through the Caribbean, churning just north of the Dominican Republic.
Projections called for Hurricane Irene to skirt the storm-killing mountains of the Dominican Republic and Haiti and continue strengthening as it approaches the Southeast United States by the weekend, said the National Hurricane Center.
Irene became a Category 2 hurricane Monday evening, with maximum sustained winds of 100 mph. The storm could become a Category 3, also known as a major hurricane, on Tuesday, when it is expected to pass near or over the Turks and Caicos and the southeastern Bahamas, forecasters said.
"The storm was already stronger than we were forecasting. We noted an upward trend in our intensity forecast. Bringing it up to a Category 3 in 24 hours when it's over the southeast Bahamas and then showing the system approaching Category 4 strength thereafter as it starts to move northwestward," said John Cangialosi, a specialist with the Miami-based Hurricane Center.
Irene grew into a hurricane early Monday, bringing heavy rain and winds to Puerto Rico, where Gov. Luis Fortuno said the storm had set off numerous landslides, brought down trees and caused at least five rivers to overflow their banks.
Some 600,000 of the island's 1 million electricity customers were without power, Fortuno said. Nearly 800 people were in shelters, but no injuries had been reported. The main airport in San Juan had reopened, but seaports in Puerto Rico and the U.S. Virgin Islands remained closed, the U.S. Coast Guard said.
CNN iReporter John Hall sent CNN video of the weather conditions in the vicinity of San Juan. Dark clouds filled the sky, as strong winds could be heard whipping against the microphone.
"I have been prepared since the start of the hurricane season with plenty of water, food, flashlights, candles and of course all my camera and video equipment," he wrote to CNN.
Elsewhere in the Caribbean, a lightning strike sparked a fire Monday that destroyed the island home of Virgin Group Chairman Richard Branson.
About 20 people, including Oscar-winning actress Kate Winslet, were in the house at the time of the fire, which broke out around 4 a.m., the media mogul said in a statement. No one was injured.
Branson said the house, located on Necker Island, the 74-acre private island the billionaire owns in the British Virgin Islands, was destroyed, along with "thousands of photographs and my notebooks."
The storm was centered about 130 miles east of Puerto Plata, in the Dominican Republic, late Monday.
Forecasters said it was likely to bring up to 10 inches of rain to the Dominican Republic and Haiti, particularly in higher elevations. Potentially dangerous flooding and mudslides were a threat, the Hurricane Center said.
The Christian aid group World Vision was prepositioning supplies and mobilizing its staff across camps in Haiti on Monday to help residents prepare for Irene.
"We are concerned that vulnerable families still living in temporary camps won't treat this storm as a serious threat after Tropical Storm Emily didn't hit Port-au-Prince as predicted," warned World Vision's Meg Sattler in Port-au-Prince. "If flooding hits, people living in unsafe housing will be the worst affected. Heavy rain has the potential to worsen sanitation conditions in camps, which, with cholera still so prevalent in Haiti, is a major concern."
As it strengthened, Irene also became larger, with tropical storm force winds extending 185 miles northeast of its center. It was moving west-northwest at about 10 mph, the Hurricane Center said.
Hurricane warnings were in effect for the north coast of the Dominican Republic, the southeastern and central Bahamas and Turks and Caicos. Hurricane watches were up for the north coast of Haiti and the northwestern Bahamas, while tropical storm warnings were in effect for much of the rest of the Dominican Republic and Haiti.
Ultimately, the storm appears headed for the United States, but where is another story, forecasters said.
The predicted track takes the storm anywhere from Florida to Virginia between Friday and Saturday.
Current predictions appear to lessen the threat to south Florida, forecasters said, although the latest Hurricane Center advisory notes that predictions this far out can be 250 miles off.
The storm is causing modest disruption to travel in the region, airlines said. American Airlines has so far canceled 32 flights as a result of the storm.
Airports in Puerto Rico and the U.S. Virgin Islands have reopened, according to the Federal Aviation Administration, and Miami International Airport is operating with only minor impacts to flights, said Marc Henderson, spokesman for the Miami-Dade Aviation Department.
Meanwhile, the remnants of tropical depression Harvey were quickly dissipating over southern Mexico on Monday. The storm came ashore near Veracruz, Mexico, on Monday with top winds of about 35 mph.
Winds were down to about 25 mph by 10 a.m. CT, the Hurricane Center said. Forecasters expect the storm to produce up to 4 more inches of rain in Veracruz, Oaxaca, Hidalgo, Puebla and Tlaxcala.
Harvey struck the coast of Belize on Sunday as a tropical storm, with top winds near 60 mph.
CNN's John Fricke, Dave Alsup and journalist Dania Alexandrino contributed to this report.