Charleston, S.C. — The first tropical storm of the season formed Saturday off the coast of South Carolina with top winds of 45 mph, but it wasn't threatening land.

Forecasters say tropical storm Alberto was centered about 140 miles east of Charleston, S.C., in the afternoon and was moving about 3 mph to the southwest.

No coastal watches or warnings were in effect, but forecasters say they may issue one later. The Miami-based National Hurricane Center says there were no hazards affecting land so far, and the tropical-strength winds weren't reaching shore. Some strengthening was possible.

"It’s not impacting us right now, but that will change over the next couple of days," said WRAL meteorologist Aimee Wilmoth. "This is certainly something we’ll have to monitor, especially if you have interests along the coastline."

North Carolina could see as much as 1 inch of rain before the tropical storm moves out of the area, according to Wilmoth.

More Info     iControl Stormtracker: Tropical Storm Alberto

National Weather Service meteorologist Sandy LaCorte in Wilmington said the system will continue its movement to the southwest before reversing course and heading northeast over the next several days.

Alberto will produce increased waves at North and South Carolina beaches, and there is a high risk of rip currents along North Carolina's Outer Banks and a moderate risk along the southeastern beaches and the entire South Carolina coast. Winds will gust to around 25 mph.

The weather service said there will be isolated and scattered rain showers along the coast of the Carolinas into early next week.

A forecast map by the hurricane center predicts that the storm will drift toward the open sea off the Midatlantic by midweek, but it's difficult to accurately predict a storm's path days in advance.

The official start to hurricane season is June 1, but tropical storms often occur before then.