Engineers north and south of the border are working to restore power to tens of thousands of homes following yesterday's snow and rain storms.
The ESB says it hopes to have power restored to thousands of homes by tonight.
The worst affected areas were Donegal, Cavan, Monaghan and the Midlands.
Motorists are asked to avoid the Sally Gap in Wicklow, which has been closed due to snow.
Driving conditions in parts of the east, north-east and midlands are also dangerous.
While the worst of the weather is thought to be over, freezing conditions are expected in many parts of the country tonight.
Up to 30,000 homes and business are still without electricity in Northern Ireland and could face several days without power.
An estimated 100,000 premises suffered power cuts over the last 24 hours according to figures from Northern Ireland Electricity (NIE).
Large areas of counties Tyrone, Derry and Antrim were lashed by blizzards, heavy rain and high winds.
Up to 300 people rescued from a mountain road after conditions overwhelmed vehicles.
NIE said: 'Damage to the network remains extensive with hundreds of faults still to be dealt with. The worst affected areas remain Omagh, Derry, Coleraine and Ballymoney. In those areas restoration of supplies is likely to take a number of days.'
The overnight weather conditions originally cut off electricity to around 50,000 homes, while snowdrifts and fallen trees closed a large number of roads.
Hundreds of passengers at Belfast International Airport spent the night in hotels because of cancelled flights.
A number of ferry sailings on the Irish Sea have been cancelled.