A jogger and a dog walker have been swept into the sea at Portstewart Strand.
The pair were on the beach when an 'unusually high' surge swept them off their feet.
The National Trust posted on one of their Twitter feeds:
"We can not stress this enough. PLEASE STAY AWAY FROM THE BEACH. Just witnessed a second person get washed away and only just escape to safety."
The fate of the other person is unknown.
A Met Office spokesperson said:"Waves will be unusually high, bringing the risk of localised flooding of roads and causeways, particularly in western and northern Scotland and northern coasts of Northern Ireland.
"Frequent wintry showers will also bring an additional hazard, mainly over higher ground. The public should be aware of the potential for disruption to travel and perhaps also power supplies."
Gales of 81mph have been reported as a weather phenomenon known as a cyclogenesis batters the UK and Ireland.
All ferry services between Belfast and Cairnryan have been suspended after a ferry collided with a terminal at Cairnryan.
No injuries have been reported.