Hurricane Irma has strengthened to a Category 5 storm and catastrophic damage is possible in the Florida Keys and southern Florida.
Irma is packing 175 mph winds as of 8 a.m. ET Tuesday, and hurricane watches have been upgraded to hurricane warnings for Puerto Rico and the Virgin Islands, the National Hurricane Center (NHC) said.
Irma is expected to continue churning with deadly hurricane-force winds and a dangerous storm surge across a wide swath of the Caribbean before moving toward southern Florida later this week.
The current NHC storm track puts Irma near the Leeward Islands, including Antigua and Barbuda, on Tuesday. Irma is on track to hit Puerto Rico and the Dominican Republic before passing over Cuba and the Bahamas and possibly approaching Florida early Sunday.
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.
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."
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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, according to the National Hurricane Center.
The Virgin 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.
Some Caribbean islands 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 Monday, 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.
ABC News' Ginger Zee, Max Golembo, Dan Peck, Armando Garcia and Josh Hoyos contributed to this report.
The Associated Press contributed to this report.