Hurricane Irma, which is heading towards the Caribbean, strengthened to a Category 5 storm on Tuesday with winds up to 175 mph, CNN reported. It is expected to reach Southern Florida in the United States on Saturday, but meteorologists fear that Puerto Rico and other islands in the Caribbean could face the storm by Tuesday night.

On Monday, when Irma developed into a Category 4 storm, the governments of Florida and Puerto Rico declared a state of emergency, according to The Guardian. The US National Hurricane Center issued warnings for many territories in the Caribbean region.

“A Hurricane warning is in effect for Antigua, Barbuda, Anguilla, Montserrat, St Kitts, Nevis, Saba, St Eustatius, Sint Maarten, Saint Martin and Saint Barthelemy, British Virgin Islands, US Virgin Islands, Puerto Rico, Vieques, and Culebra,” its latest advisory said. Many other islands in the Caribbean have also been asked to prepare for the intensifying storm.

At 11 pm Atlantic Standard Time on Monday, Irma was about 660 km east of the Leeward Islands. It was packing maximum sustained winds of 220 kph and was heading west 20 kmph.

“We’re looking at Irma as a very significant event,” said Executive Director of the Caribbean Disaster Emergency Management Agency Ronald Jackson. “I can’t recall a tropical cone developing that rapidly into a major hurricane prior to arriving in the Central Caribbean.”

Irma comes on the heels of Hurricane Harvey, which made landfall in Texas on August 26 and has killed at least 35 people, so far.