The hurricane warnings remain in place as this slow-moving and powerful storm is set to strike the US.

Hurricane Dorian continued to move north early on Thursday, running parallel to the coast of the southeast United States with a turn to the northeast expected later in the day.

It has increased in strength and is now a Category 3 storm on the Saffir Simpson Scale, with sustained winds of 185 kilometres per hour and is set to remain a powerful storm before it makes landfall overnight Thursday along the North Carolina coast.

Not only has Dorian strengthened, but it has also grown in size and stretches 800km across, which means the torrential rains and damaging winds will reach a long way inland.

Hurricane-force winds will be felt close to 100km from the centre of the storm and tropical storm-force winds will reach outwards to 280km. Winds of this strength may cause widespread tree damage and power outages, along with damage to some buildings.

Dorian is moving fairly slowly at 11km/h, so the flooding rains will be slow to move away, with some areas seeing as much as 400mm of rain over the next 24 hours.

As well as the heavy, persistent rains, storm surge is a big concern along coastal areas from Georgia up to North Carolina, with as much as 2.1 metres of storm surge above high tide levels expected in some areas. Charleston in South Carolina is one of several cities that are likely to suffer significant storm surge.

Some roads to the barrier islands in the region will be cut off due to high water and powerful winds.

Once Hurricane Dorian has made landfall along the coast in North Carolina, it is expected to make a turn to the northeast and pick up speed, taking it further away from land. However, the winds will then turn to the northwest, forcing the seawater towards the Outer Banks, which could cause significant coastal flooding.

The end of the week will see Dorian bring rain, wind and coastal problems to the mid-Atlantic and New England. The storm may then move across Nova Scotia and Newfoundland, Canada, through the weekend.