Erin is a strong Category 3 hurricane, the National Hurricane Center said in its 8 p.m. ET update Sunday, with sustained winds of 125 mph and tropical storm-force winds reaching out 205 miles. The storm is just over 300 miles northwest of Puerto Rico as of Sunday evening.

Erin is the first hurricane to develop over the Atlantic this year, and meteorologists are closely tracking its path and forecast.

The storm will remain a major hurricane through the middle of the week, according to the National Hurricane Center.

At the start of the storm, Hurricane Erin was gauged as high as a catastrophic Category 5 storm with a wind speed of 240 km/h but later was downgraded to Category 4 and then to Category 3.

An eyewall replacement cycle is underway within Hurricane Erin as the monster storm continues to barrel across the Atlantic while bringing gusty winds and rain to Puerto Rico and the Virgin Islands after rapidly intensifying into a catastrophic Category 5 hurricane over the weekend.

Erin, which quickly strengthened into a Category 5 storm on Saturday, is not expected to make landfall in the U.S., but experts remain on alert.

Despite this, the US National Hurricane Center (NHC) says Erin is growing in size, with tropical-storm-strength winds extending 205 miles from its centre. Storm-related hazards, including flash flooding and landslides, are expected in the Virgin Islands and Puerto Rico.