More than 33 million Americans were under coastal flood advisories on Aug 20 as Hurricane Erin head north toward the U.S. mainland.

Meteorologists are closely tracking the projected path and forecast of Hurricane Erin, which is the first hurricane to develop over the Atlantic this year.

Weather conditions are expected to deteriorate along the coast of North Carolina on Aug. 20 due to Hurricane Erin, according to the NHC.

Erin may strengthen into a major Category 3 hurricane Wednesday night, forecasters say. The worst impacts at the Jersey Shore will occur on Thursday.

Even more significant is Erin’s massive size. Forecasters say hurricane-force winds are now stretching out as far as 105 miles from Erin’s center, and tropical storm-force winds extend outward to 265 miles.

Hurricane Erin will eventually track eastward in the North Atlantic towards the United Kingdom. But crucially it will weaken and no longer be a hurricane or tropical storm before it brings the UK any impacts.