Isaac gave South Floridians a stormy Sunday night but resolutely remained a Tropical Storm, even in the Florida Keys, saving its wallop for somewhere along the coast of the Gulf of Mexico.

The National Hurricane Center’s 8 p.m. advisory showed the center of Isaac moving into the southeastern Gulf of Mexico, hours after it took a slight shift west to spare South Florida a more severe storm. The storm actually dipped a bit in strength of sustained winds to 60 mph as it skirted Key West in the late afternoon.

Mainland South Florida got some powerful gusts — 64 mph was recorded at Port Everglades in Fort Lauderdale — but the strongest part of the storm really only impacted the Lower Keys and it, too, was slightly weaker than expected.

Outside Key West’s ramshackle inside-outside Schooner Wharf Bar, a bearded bicyclist pedaled by, wearing a rain poncho and passing the word.

“It’s not a hurricane,” the cyclist called out. “It’s a windy day in paradise.”

The Hurricane Center predicted the storm would strengthen as it moved north into the Gulf of Mexico, with tracks predicting it would reach hurricane strength late Monday or early Tuesday, and placed the coast from New Orleans to Destin, Fla., under a hurricane warning.

A Flood Watch remained in effect across all of South Florida, the National Weather Service said in its 8 p.m. report. It would continue through Monday evening, the NWS said, because Isaac’s rain bands would continue throughout the night. “Additional rainfall amounts of 1 to 3 inches are possible tonight into Monday, which can lead to some flooding over South Florida,” the 8 p.m. NWS advisory said.

The storm left power outages in its wake: In Miami-Dade, 9,730 customers were without power at 10 p.m. Sunday, Florida Power & Light reported on its website. In Broward, 6,250 customers were without power and 2,300 Palm Beach residents lost electricity, too.

With most schools closed on Monday, South Floridians were advised to head out cautiously, if at all, so city workers could clean up debris and check basic services that were shut down for the storm on Sunday.

Tri-Rail, for example, announced no service Monday, time for engineers to do track inspections and maintenance in order to resume service on Tuesday.

“We always have people get injured or killed post-storm,” Broward Emergency Operations Director Chuck Lanza said Sunday afternoon, urging people to stay inside.

CAUTION ADVISED

He reminded pedestrians to keep clear of puddles and motorists to be extra cautious on the soaked and debris-strewn roadways. “If you can stay home and do things around the house, that’s the best idea,” he advised Sunday afternoon, once Isaac had passed with no immediate reports of extreme flooding or severe damage.

Isaac also grounded some 765 flights in and out of South Florida: 555 at Miami International Airport and 160 flights at Fort Lauderdale. Key West’s airport was closed all day, forcing cancellation of about 50 flights.

The top wind speed record in the Keys was a 70 mph gust at the Smith Shoal Light about 11 miles northwest of Key West. Nothing stronger was expected as Isaac begins moving away from the island chain.

“It looks like it’s going to be diminishing impacts over the next couple of hours,” said Mike Rapsik, senior forecaster at the National Weather Service’s Key West office, just before 5 p.m. More squalls and rains bands could continue sweeping the island through the morning hours Monday.