Hurricane Irma strengthens to Category 4, 'increasing chance' could affect Florida- NHC

Hurricane Irma has strengthened to a Category 4 storm today, and the National Hurricane Center said there is an "increasing chance" that Florida and the Florida Keys will see "some impacts from" Irma later this week and weekend, though it's still too early to determine what direct effects it may have.

Florida Gov. Rick Scott on Monday declared a state of emergency for every county to ensure that local governments have enough "time, resources and flexibility to get prepared for this dangerous storm," according to a statement from his office.

The official forecast track includes parts of south Florida, including Miami.

Scott said in the statement that Irma is a "life-threatening" storm and Florida "must be prepared."

"In Florida, we always prepare for the worst and hope for the best," Scott said, "and while the exact path of Irma is not absolutely known at this time, we cannot afford to not be prepared."

The storm -- which is currently closing in on the Caribbean with winds up to 130 mph -- is expected to be near the Cuba coast by Saturday.

The storm is expected to strengthen over the next 24 hours as it moves west, with winds of 150 mph as it impacts portions of the Leeward Islands on Tuesday.

Tuesday afternoon and evening rain and winds are expected to move into the northern Leeward Islands, including Antigua and Saint Martin, with the worst conditions occurring Tuesday night into early Wednesday morning.

Hurricane warnings -- which are usually issued 36 hours before the anticipated first occurrence of tropical-storm-force winds -- are in effect for Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, Nevis, Saba, St. Eustatius,

Sint Maarten, Saint Martin and Saint Barthelemy as of 11 a.m. ET, according to the National Hurricane Center.

The Virgins Islands and Puerto Rico are forecast to see deteriorating conditions throughout the day on Wednesday with the worst of the rain and wind arriving Wednesday night.

Hurricane watches -- which typically are issued 48 hours before the anticipated first occurrence of tropical-storm-force winds -- have been issued for the U.S. Virgin Islands, the British Virgin Islands, Puerto Rico, Vieques, Culebra and Guadeloupe.

Some Caribbean island were making preparations as the storm approached.

In Puerto Rico, a state of emergency has been declared that activates the National Guard.

At a news conference today Puerto Rico Gov. Ricard Rossello warned of flooding and power outages.

He canceled classes for Tuesday and declared a half-day of work for the U.S. territory, and said the government was preparing 456 shelters on the island, which can house 62,000 people.

In Antigua, Prime Minister Gaston Browne recommended taking preventative measures, like cleaning drains, The Associated Press reported Sunday. Workers were also seen pruning trees and shrubs to help keep them from tearing down phone and power lines, the AP said.

In a statement, Browne said while "the passage of a hurricane is not a matter to be taken lightly ... we must not panic," according to the AP.

ABC News' Ginger Zee, Max Golembo, Dan Peck, Armando Garcia and Josh Hoyos contributed to this report.

The Associated Press contributed to this report