After pounding South Florida with heavy rain and strong winds Monday, Tropical Storm Gordon is gaining strength and taking aim at the Gulf Coast.

The National Hurricane Center issued a hurricane warning from the mouth of the Pearl River, which separates southern Mississippi from the easternmost part of Louisiana, to the Alabama-Florida border.

Gordon formed into a tropical storm near the Florida Keys early Monday as it headed west-northwest at 17 mph. The storm is expected to reach hurricane strength when it hits the Gulf Coast by late Tuesday night. From there, it is forecast to move inland over the lower Mississippi Valley on Wednesday.

Rolling past the west coast of Florida, some 95 miles from Fort Myers by 8 p.m. EDT, Gordon had maximum sustained winds of 60 mph. The storm is expected to gather strength while making its way through the Gulf of Mexico.

Parts of the Gulf Coast could get up to eight inches of rain through Thursday.

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The hurricane center also issued a storm surge warning, meaning possible "danger of life-threatening inundation,'' for late Tuesday for the area stretching from Shell Beach, Louisiana, to Dauphin Island, Alabama.

“The deepest water will occur along the immediate coast near and to the east of the landfall location, where the surge will be accompanied by large waves,” the center said.

Louisiana Gov. John Bel Edwards declared a state of emergency Monday and said 200 National Guard troops will be deployed to the southeastern part of the state.

Although Louisiana lies just outside the hurricane warning area, authorities in New Orleans issued a voluntary evacuation order for areas outside the city’s levee protection system, including the Venetian Isles, Lake Saint Catherine and Irish Bayou areas.

Strong wind gusts, battering waves, above-normal tides, minor coastal flooding, flash flooding and a couple of isolated tornadoes and waterspouts will be the main threats from the storm, AccuWeather said.

Parts of the northern Gulf Coast could see 3-6 inches of rainfall Tuesday into Wednesday, from southeast Louisiana into far southern Mississippi and far southern Alabama, according to the Weather Channel. Localized totals of six inches or more are possible in some areas.

The storm should make landfall with winds of about 60 mph. However, it could still reach hurricane status, which would be 74 mph, AccuWeather said.

"Any strong tropical storm has the potential to strengthen to a hurricane even when that storm may only spend a day or two over warm waters," AccuWeather meteorologist Alex Sosnowski said.

Miami Beach police said via Twitter that the Labor Day holiday was “NOT a beach day” because of rough surf and potential rip currents. Red flags flew over Pensacola-area beaches in Florida’s Panhandle, where swimming and wading in the Gulf of Mexico were prohibited.

The weather delivered a blow to businesses during the holiday weekend.

Jenna Wright, owner of a coffee shop in Naples, Florida, told the Naples Daily News that she expected higher numbers for the Labor Day weekend.

“This is normally a decent weekend, but the storm and red tide aren’t helping,” Wright said. “We’re a beach coffee shop, and if people can’t go to the beach, then we won’t get any customers.”

Gordon is the seventh named tropical storm or hurricane to form in the Atlantic basin this year.

Storm tracker:Track Tropical Storm Gordon

Tropical Storm Florence continues to spin in the central Atlantic Ocean, about 2,700 miles from Miami. Florence will rotate harmlessly in the central Atlantic this week but could pose a threat to Bermuda and/or the U.S. East Coast in the next six to 12 days, according to Weather Underground meteorologist Bob Henson.

Contributing: The Associated Press