SAN JUAN, Puerto Rico >> Officials across the northeastern Caribbean canceled airline flights, shuttered schools and urged people to hunker down indoors as Hurricane Irma barreled toward the region as a powerful Category 4 storm expected to strengthen more before nearing land late Tuesday.

States of emergency were declared in Puerto Rico, the U.S. Virgin Islands and all of Florida while people on various Caribbean islands boarded up homes and rushed to find last-minute supplies, forming long lines outside supermarkets and gas stations.

Irma had maximum sustained winds of 140 mph late Monday, the U.S. National Hurricane Center said. It was centered 410 miles east of the Leeward Islands and moving west at 13 mph.

Authorities warned that the storm could dump up to 10 inches of rain, cause landslides and dangerous flash floods and generate waves of up to 23 feet.

“This is not an opportunity to go outside and try to have fun with a hurricane,” U.S. Virgin Islands Gov. Kenneth Mapp warned. “It’s not time to get on a surfboard.”

The storm’s center was expected to move near or over the northern Leeward Islands late Tuesday and early Wednesday, the hurricane center said.

Residents on the U.S. East Coast were urged to monitor the storm’s progress in case it should turn northward toward Florida, Georgia or the Carolinas.

“This hurricane has the potential to be a major event for the East Coast. It also has the potential to significantly strain FEMA and other governmental resources occurring so quickly on the heels of (Hurricane) Harvey,” Evan Myers, chief operating officer of AccuWeather, said in a statement.

In the Caribbean, hurricane warnings were issued for 12 island groups, including Antigua, where the governor urged people to evacuate the tiny island of Anegada if they could ahead of the storm.

Vivian Wheatley, proprietor of the Anegada Reef Hotel, planned to stay behind. She said she would hold up in one of the hotel rooms and take advantage of the generator since there were no guests.

“We know it’s a very powerful (storm), and we know it’s going to be very close,” she said. “Let’s hope for the best.”

People in the U.S. territory of Puerto Rico braced for electricity outages after the director of the island’s power company predicted that storm damage could leave some areas without electricity for four to six months. But “some areas will have power (back) in less than a week,” Ricardo Ramos told radio station Notiuno 630 AM. The utility’s infrastructure has deteriorated greatly during a decade-long recession, and Puerto Ricans experienced an island wide outage last year.

Both Puerto Rico and the U.S. Virgin Islands expected 4 inches to 8 inches of rain and winds of 40-50 mph with gusts of up to 60 mph.

A hurricane warning was posted for Antigua and Barbuda, Anguilla, Montserrat, St. Kitts and Nevis, St. Martin, Saba, St. Eustatius, St. Maarten and St. Barts, Puerto Rico, and the U.S. and British Virgin islands. A tropical storm warning was in effect for Guadeloupe and a tropical storm watch for Dominica.