KEY WEST, Florida (AP) — Tropical Storm Isaac started pelting the Florida Keys with rain and strong winds today, and it could strengthen into a dangerous hurricane by the time it starts hitting the northern Gulf Coast in coming days.

Exactly where Isaac would hit once it passed the Keys remained highly uncertain, with forecasters saying hurricane conditions could reach anywhere from the New Orleans metro area to the Florida Panhandle by Tuesday. And the storm is large: tropical storm conditions extend more than 200 miles from the storm's centre, meaning Isaac could cause significant damage even in places where it does not pass directly overhead.

Isaac has brought havoc to the Caribbean already, killing seven people in Haiti and downing trees and power lines in Cuba. And it had officials worried enough in Tampa that they shuffled around some plans for the Republican National Convention.

However, Isaac had yet to create a panic in South Florida. In Miami Shores, some residents said they hadn't even put up storm shutters. Edwin Reeder, 65, stopped by a gas station to pick up some drinks and snacks. He didn't bother topping up his car's half-full fuel tank.

Reeder said he hadn't put up storm shutters, instead just clearing his gutters so all the water could drain.

"This isn't a storm," he said. "It's a rain storm."

On Key West, locals followed time-worn storm preparedness rituals while awaiting the storm after Isaac swamped the Caribbean. Hundreds of flights were canceled Sunday as the storm bore down.

A steady line of cars moved north Saturday along the Overseas Highway, the only road linking the Florida Keys. Residents boarded up windows, laid down sandbags and shuttered businesses ahead of the approaching storm. Even Duval Street, Key West's storied main drag, was subdued for a weekend, though not enough to stop music from playing or drinks from being poured.

"We'll just catch every place that's open," said Ted Lamarche, a 48-year-old pizzeria owner visiting Key West to celebrate his anniversary with his wife, Deanna. They walked along on Duval Street, where a smattering of people still wandered even as many storefronts were boarded up and tourists sported ponchos and yellow slickers.

"Category None!" one man shouted in a show of optimism.

The Keys were bracing storm surge of up to four feet, strong winds and the possibility of tornadoes. The island chain's two airports closed Saturday night, and volunteers and some residents began filing into shelters.