The latest hurricane that could threaten the U.S. continued to intensify on Monday, though its future path remains unclear.

Hurricane Irma was upgraded to a category 4 storm and was expected to continue to strengthen over the following 48 hours, according to the National Hurricane Center.

The National Weather Service Charleston said Tuesday morning that the risks for some sort of impact from Irma on South Carolina are increasing although specifics are not known.

A strengthening storm

The storm packed 150 mph winds and was located 450 miles east of the Leeward Islands, which form the outer portion of the Caribbean, the Hurricane Center said.

Forecasters say it's becoming more likely to see impacts from Irma in the Florida Peninsula and the Florida Keys, although that is not certain. Any impact on South Carolina or other parts of the East Coast is still too early to know.

"We're looking at Irma as a very significant event," Ronald Jackson, executive director of the Caribbean Disaster Emergency Management Agency, said by phone. "I can't recall a tropical cone developing that rapidly into a major hurricane prior to arriving in the central Caribbean."

Residents in the eastern Caribbean are already preparing as emergency officials warned on Monday that Irma could dump up to 10 inches of rain, unleash landslides and dangerous flash floods and generate waves of up to 23 feet as the storm draws closer.

U.S. residents were urged to monitor the storm's progress in case it turns northward toward Florida, Georgia or the Carolinas.

Florida Gov. Rick Scott declared a state of emergency ahead of the storm, according to multiple media outlets. Scott's declaration followed a similar order by Puerto Rico's Gov. Ricardo Rosselló, also made on Monday.

The hurricane center forecast maintains Irma as a powerful hurricane during the next 5 days.

Charleston Weather

Although the forecast models made some impact on the U.S. more likely on Sunday, the exact path and any impact on South Carolina or Charleston is not known.

Regardless, anyone in a storm prone area is urged to have a plan in place since it is the height of hurricane season.

Bob Bright, a meteorologist with the National Weather Service's Charleston office took to Facebook live Monday night with a brief, informational broadcast. 

In the video, Bright emphasized that it was till too early to tell what impact Irma could have on South Carolina.

While the storm is expected to have some impact on the mainland U.S., the forecast gets less and less accurate the further out it goes, he said. 

Bright urged residents to visit the Hurricane Center's and the Weather Service's websites for updates and storm preparedness tips.

Residents should be sure they have enough food and water, and be sure they have any medications they need whether they plan to evacuate or not, he said. Everyone should think about an evacuation plan and think about what steps they need to take to secure their home from damage.

"We really just don't want you to panic, but we want you to be informed and get prepared just in case," Bright said. "Preparation is the key."

Watches and warnings

A hurricane warning was issued for Antigua and Barbuda, Anguilla, Montserrat, St. Kitts and Nevis, St. Martin, Saba, St. Eustatius, St. Maarten and St. Barts.

A hurricane watch was in effect for Puerto Rico, Vieques, Culebra, the British and U.S. Virgin islands and Guadeloupe. A tropical storm watch was issued for Dominica.

Projected path and location

Irma was moving west around 13 mph, the Hurricane Center said. The system was expected to continue in that general direction before making a turn to the west-northwest late Tuesday.

How strong is the storm?

The satellite presentation of Irma has improved markedly over the past 24 hours, with the eye becoming larger and much more distinct, the Hurricane Center said.

"This hurricane has the potential to be a major event for the East Coast. It also has the potential to significantly strain FEMA and other governmental resources occurring so quickly on the heels of (Hurricane) Harvey," Evan Myers, chief operating officer of AccuWeather, said in a statement.

The Associated Press contributed to this report.