The Florida Department of Transportation announced Saturday that it is reopening the 14-mile stretch of Interstate 75 that was shut down due to rising river water under the highway. Officials said the Myakka River's water levels had receded enough to safely reopen the highway.

But, officials warned they may have to shut down the interstate again if water levels rise once more.

Officials had shut down I-75 from mile marker 179, near North Port and Toledo Blade Blvd. to mile marker 193, near Jacaranda Blvd, and long detours were in place.

I-75 is the main highway on the west coast of Florida and is a main route for travelers between Tampa-St. Petersburg and Fort Myers and Naples.

The Centers for Disease Control and Prevention put out a health advisory to healthcare professionals treating patients in areas affected by Hurricanes Fiona or Ian, telling them to maintain a high index of suspicion for carbon monoxide poisoning.

"Other people who may have been exposed to the same CO source may need to be identified and evaluated," the CDC said in a health advisory.

-ABC News' Eric Strauss

Four people have died in North Carolina since Friday in storm-related incidents, state officials said Saturday.

Two people died due to car accidents caused by storm conditions, one man drowned in his car and a fourth man died due to carbon monoxide poisoning from a generator.

Among those killed was a 25-year-old man who lost control of his vehicle and hydroplaned into another vehicle, a 24-year-old woman whose vehicle went off a wet road and struck a tree and a 22-year-old man who drowned when his truck left the roadway and submerged in a flooded swamp.

A 65-year-old man died Saturday from carbon monoxide poisoning from a generator running in his closed garage while the power was out. His wife was hospitalized.

“The storm has passed, but many hazards remain with downed trees, downed power lines and power outages,” said North Carolina Gov. Roy Cooper in a press release. “We mourn with the families of those who have died and urge everyone to be cautious while cleaning up to avoid more deaths or injuries.”

A flood watch remains in effect in parts of Virginia and West Virginia on Saturday as Ian’s remnants push north.

The storm is significantly weakened, but winds may still top 35 mph as rain covers the Mid-Atlantic and Northeast this weekend.

-ABC News’ Daniel Amarante

Tropical Storm Ian has weakened slightly, but it is expected to not only strengthen but rapidly intensify overnight as it travels over warm waters in the Caribbean.

As of 5 p.m. ET, the storm system had maximum sustained winds of 45 mph and was moving west-northwest at 12 mph, with the center located about 220 miles away from Grand Cayman.

Dry air ahead of the storm has delayed the strengthening trend so far. But the rapid intensification is expected to occur Monday into Tuesday as the system continues across the northwestern Caribbean and closes in on western Cuba.

Over the next 24 hours, the outer bands will impact Jamaica and the Cayman Islands, bringing rounds of heavy rain, possible flash flooding and storm surge. Later Monday and into Monday night, Ian will be closing in on western Cuba and will likely bring significant wind and storm surge impacts to the region.

A hurricane warning is in effect for Grand Cayman and portions of western Cuba. A tropical storm watch has been issued for portions of western Cuba, as well as the lower Florida Keys, including Key West.

As of 5 p.m., the forecast track was nudged slightly eastward. Overall, the forecast guidance variability and uncertainty will remain high, and the track for where the storm will be from the middle to the end of the week will continue to shift over the next 24 to 48 hours.

-ABC News' Dan Peck