Cold weather is forecast throughout this week but Met Éireann has said temperatures will remain higher than in Britain.
The British Met Office has told people to prepare for temperatures to drop to about -10 degrees in rural areas of Scotland tonight, while parts of northern and eastern England are bracing themselves for temperatures as low as -5 degrees.
"We are on a battleground of very cold weather to the east and mild weather to the west," Met Éireann forecaster Joan Blackburn said this morning.
Outbreaks of rain and sleet are expected to give way to clearer weather and some sunny spells today, but scattered showers of rain and hail should also follow.
Tonight will be cold with widespread frost. Snow is possible later in the week, especially in areas of high ground in the north and east, but cold rain is more likely, Ms Blackburn said.
Tomorrow is due to be very cold, but Ms Blackburn stressed the week's weather forecast was "not at all clear cut" and was changing on a "day-to-day basis."
Motorists have been advised to exercise extreme caution this week, with a strong likelihood of icy road conditions.
The cold snap is expected to end by the weekend, when a slight rise in temperatures is expected.
