Florida Gov. Rick Scott announced Sunday that he had declared a state of emergency in 26 counties in the state's Panhandle and Big Bend regions as forecasters predicted Tropical Storm Michael would make landfall as a Category 2 hurricane later this week.

Scott also announced that he was activating 500 members of the Florida National Guard to assist with planning, logistics and storm response.

"This storm will be life-threatening and extremely dangerous," said Scott, who also warned of hurricane-driven storm surge that could affect most of the state: "If this storm hits Panama City, Tampa could still have storm surge."

As of 5 p.m. Sunday, the Miami-based National Hurricane Center said Michael had maximum sustained winds of 50 miles per hour and warned that the threat to residents along the northeastern U.S. Gulf Coast was "increasing." The forecast called for the storm's eye to move across the eastern Gulf of Mexico between Monday night and Tuesday night and approach the Gulf Coast on Wednesday.

The storm was about 130 miles southeast of Cozumel, Mexico and moving north-northeast at about 3 mph. Tropical storm winds extended out 205 miles, primarily east of the storm's center.

The north Florida city of Tallahassee on Sunday opened two locations where residents could get sandbags in case of flooding.

"While the impacts are still uncertain, our area could experience increased wind activity and heavy rainfall, which could cause localized flooding and downed trees," Tallahassee officials said in a statement.

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Tallahassee Mayor Andrew Gillum, who is the Democratic nominee for governor, had planned to campaign in South Florida Monday and Tuesday, but he said he would return to Tallahassee to help with storm preparations.

The city of Pensacola tweeted to residents, "Be sure you have your emergency plan in place."

A tropical storm warning was in effect for the Cuban provinces of Pinar del Rio and the Isle of Youth as well as the coast of Mexico from Tulum to Cabo Catoche. A warning indicates tropical storm conditions are expected, in this case, within 24 hours.

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An Air Force hurricane hunter airplane was sent into the storm to investigate, the hurricane center said.

Michael is the 13th named storm of the 2018 hurricane season, according to hurricane center spokesman Dennis Feltgen.

The Associated Press contributed to this report.