Up to 9 inches of rain was possible in North Carolina and Virginia, along with life-threatening flash floods.
The storm killed at least one person in Florida and another, an 11-year-old girl, in Georgia.
Here is what to expect and when across the South and East CoastA Category 4 landfall
Michael made landfall Wednesday afternoon in the Florida Panhandle near Mexico Beach and Panama City.
As Michael approached the Florida coast, its pressure dropped to about 919 millibars (mb). The lower the pressure, the more intense the storm. Hurricane Katrina in 2005 made landfall with a pressure of 920 millibars.
Michael made landfall as a Category 4 with whopping 155 mph winds. A hurricane reaching 157 mph is in the highest category, a Category 5.
Described by Florida Gov. Rick Scott as "monstrous," Michael was the worst storm to hit the Florida Panhandle region since the mid-1800s and the first Category 4 hurricane to come ashore in the region on record.
As cleanup and rescues were underway Thursday, Gov. Scott urged residents who evacuated and hunkered down at home to stay off the roads.
Among those helping were about 450 Florida Highway Patrol officers, many of whom drove through the night to the Panhandle to aid with rescues.
Michael has now weakened to a tropical storm and is moving quickly north.
The storm was near Charlotte on Thursday morning.
Tropical storm warnings were in effect from Georgia to North Carolina, including Savannah, Raleigh, Wilmington and Charleston.
Up to 9 inches of rain could drench Virginia and North Carolina.
North Carolina is still recovering from last month's Hurricane Florence which dumped massive amounts of rain and caused behind deadly flooding -- and could face rain in those same areas.
For North Carolina, "Michael isn't as bad as Florence but adds insult to injury," Gov. Roy Cooper said at a news conference Thursday.
Six inches of rain has already hit the state from Michael with more to come, Cooper said
"The ragged but raging remains of Hurricane Michael is over us," the governor warned.
Tornadoes are also possible Thursday in North Carolina and Virginia.
But it's not just the South in the storm's path. Thursday afternoon a cold front will push east combining its heavy rain with Michael's moisture, threatening flash flooding from Washington, D.C., to New York City to Boston.
Flood watches are in effect from Georgia to Vermont.
By Thursday night, some heavy rain from Michael will brush through Long Island and New Jersey, where flash flooding is possible.
Some areas as far north as southern New Jersey could see up to 6 inches of rain.
By mid-Friday morning, the entire storm system will push off the East Coast.