Weather Channel meteorologist Kevin Roth warned the system could bring a storm surge of up to 3 feet to the areas between Apalachicola and Tampa in northwestern Florida.
"But there could be a few spots that could go up to 4 or 5 [feet] and this part of this coastline is susceptible to flooding," he added.
After that, the storm would head across Florida and "brush the entire Southeast coastline with rain, beach erosion and windy conditions on Friday," according to NBC meteorologist Bill Karins.
As of 8 a.m. ET, a hurricane watch was in effect from Florida's Anclote River to Indian Pass — with a tropical storm warning in effect from the former to the Walton/Bay County line.
Meanwhile, North Carolina's Outer Banks will likely be drenched as a tropical weather system blows by with up to 5 inches of heavy rain, forecasters said.
Karins warned of rough surf and dangerous rip currents off of North Carolina as so-called Tropical Depression 8, which had glanced the coastline late Tuesday, headed back out into the Atlantic. The storm system had maximum sustained wind speeds of 35 mph and was moving northeast at 5 mph early Wednesday.
In the Pacific, Category 1 Hurricane Madeline churned toward Hawaii, promising to bring heavy rain and high winds. Category 4 Hurricane Lester followed roughly Madeline's path and toward the archipelago. It was forecast to hit over the weekend, according to the National Weather Service.
"Madeline is going to pass dangerously close to the Big Island of Hawaii late today into Thursday morning Hawaiian time," Karins said early Wednesday.
The storm was expected to be a Category 1 hurricane on its closest approach to Hawaii's main island, and minor wind damage along with threat of flash flooding, he said. Between 5 and 10 inches of rain were expected with higher amounts in some areas.
It could be the first Pacific hurricane to make landfall in that state in decades. Hawaii public schools were closed Wednesday and Thursday in anticipation of severe weather.