Residents in the Carolinas were advised to prepare for “life-threatening storm surge” as Tropical Storm Isaias crept up the coast and was expected to make landfall with the force of a hurricane by Monday night.

“Isaias is forecast to regain hurricane strength before it reaches the coast of northeastern South Carolina and southern North Carolina, and hurricane conditions are expected in the hurricane warning by this evening. Preparations should be rushed to completion,” the National Weather Service warned Monday morning. “There is the danger of life-threatening storm surge inundation along portions of the immediate coastline and adjacent waterways of northeastern South Carolina and southern North Carolina coast.”

Those areas could expect up to 8 inches of rain, flash flooding and possible tornadoes.

Isaias was expected to make landfall near the border of the Carolinas between 10 p.m. Monday and 2 a.m. Tuesday as a Category 1 hurricane or a strong tropical storm. Meteorologists worried the landfall would coincide with the high tide.

Coastal areas north of the Carolinas could also expect possible “flash and urban flooding, high winds, dangerous storm surge, coastal flooding, life-threatening surf, rip currents, and severe thunderstorms with tornadoes to portions of the Eastern U.S.,” the weather service said.

About 59 million people were under a tropical storm alert Monday, stretching from Florida to Maine. Most of those areas were also under flash flood watches, as heavy rainfall was predicted.

The storm had already dropped heavy rain on Florida’s east coast even though it had been downgraded from a hurricane to a tropical storm Saturday afternoon.

Last week, the storm uprooted trees, destroyed crops and homes and caused widespread flooding and small landslides in the Dominican Republic and Puerto Rico. One man died in the Dominican Republic. In Puerto Rico, the National Guard rescued at least 35 people from floods that swept away one woman, whose body was recovered Saturday.

Isaias snapped trees and knocked out power as it blew through the Bahamas on Saturday. Officials there opened shelters for people in the Abaco Islands to help those who have been living in temporary structures since Hurricane Dorian devastated the area, killing at least 70 people in September 2019.

Elisha Fieldstadt

Elisha Fieldstadt is a breaking news reporter for NBC News.

Associated Press contributed.