Storm Eowyn has hit Great Britain. Schools and railways have been closed.
Flights from Glasgow, Edinburgh and Dublin airports have been cancelled.
Around 4.5 million people in parts of Northern Ireland and Scotland were sent an emergency alert on their mobile phones on Thursday evening. Meanwhile, Northern Ireland is braced for the strongest winds since 1998, police said.
"The emergency alert system will send a message to every compatible phone in the most at-risk areas," authorities warned.