A nasty coastal storm, known as a nor’easter, is organizing and strengthening off the Southeast US.

The storm is poised to deliver tropical storm-force wind gusts, soaking rain and dangerous seas up most of the East Coast into early next week.

It’s packing a serious punch as it strengthens and moves north. Gusty winds and rain are already hitting parts of the mid-Atlantic. Gusts over 30 mph have been measured near the North Carolina coast. Portions of North Carolina Highway 12 in the Outer Banks were closed due to heavy ocean overwash on Saturday.

But the worst conditions will start to unfold Sunday.

Water levels along the New Jersey, Delaware, Maryland and Virginia coasts could rise to levels not seen in nearly a decade. The major coastal flooding could inundate roads and homes and cause beach erosion alongside the heavy rain and potentially damaging wind.

It could become an air travel nightmare for major hubs like Washington, DC, New York City and Boston with strong winds likely causing delays and cancellations by Monday.

A state of emergency will go into effect for New Jersey Saturday night ahead of the storm’s worst impacts, acting Gov. Tahesha Way announced Friday.

“I urge all New Jerseyans to exercise caution, monitor local weather forecasts and warnings, stay informed on evacuation protocols, and remain off the roads unless absolutely necessary,” Way said in a statement.

The nor’easter already caused some impacts: It drove the highest tides of the month even higher on Friday in parts of the Southeast. Officials in Charleston, South Carolina, made multiple city parking garages free while urging people in low-lying areas to move their vehicles as ocean water flowed onto land.

The storm’s most serious threat

A significant coastal flooding event is unfolding from the Outer Banks through the Northeast with tide levels this weekend just shy of their highest marks of the month. The combination of soaking rain and strong winds pushing water onshore will be potent: Dozens of coastal spots from North Carolina to New York are expected to reach moderate-to-major flood stage from this nor’easter.

In Delaware and New Jersey, particularly the southern part of the state, coastal flooding could get bad enough to cause some roads to become impassible and some structures to flood, according to the National Weather Service in Mount Holly, New Jersey.

Water levels could rise above 8 feet Atlantic City, New Jersey — the highest level since Sandy in 2012 — and enter major flood stage on Sunday afternoon. That’s enough to trigger widespread flooding of roads in the area with some neighborhoods potentially becoming cut off due to the water, according to NOAA.

The nor’easter is also driving turbulent seas and generate rough surf that will make swimming dangerous for hundreds of miles of coastline.

Not just a coastal flood concern

Up to half a foot of rain could fall near the North Carolina coast this weekend, paired with gusty winds up to 45 mph. The nor’easter will also contribute to ongoing beach erosion in the state’s Outer Banks, where at least nine unoccupied homes have collapsed into the Atlantic since September 30 due to intense wave action and erosion from recent storms.

Disruptive weather will reach farther north Sunday and Monday with a few inches of rain possible along the rest of the mid-Atlantic coast and into southern New England. Any areas caught under multiple rounds of this drenching rain could see localized flash flooding.

Climate change is supercharging the winds of the strongest Nor’easters, a recent study found, and this one will be no slouch.

Powerful winds, with possible prolonged gusts of 40 to 50 mph, will accompany this rain. Winds will max out into Sunday for much of the Southeast and parts of the mid-Atlantic coast. New Jersey and southern New England will feel some of the strongest gusts — up to 60 mph — Sunday into Monday. These wind gusts are as strong as what a tropical storm produces, despite this system not being one.

Power outages are possible as these strong winds batter coastal areas. Less powerful, but still noticeable winds should also stretch further inland to more heavily populated areas.

After the storm moves away from the coast later Monday into Tuesday, the East could get a brief reprieve from the dreary weather. Warmer-than-average temperatures are expected to return to much of the region later in the week.