Many parts of the country are waking up to snow this morning after wintry showers overnight.
There is a yellow snow-ice warning in place until Saturday.
Met Éireann says there will be widespread frost at night with icy stretches on untreated surfaces.
Met Éireann's John Eagleton says the greatest risk of snow showers will be overnight tomorrow and Thursday.
"The big threat of snow this week remains late on Wednesday night/Thursday," said Mr Eagleton.
"The winds turn easterly and a depression to the south of Ireland injects a lot of moisture into those easterly winds.
"So that's the potential for a good bit of snow."
Tonight will see rain, sleet and snow "affect much of the southern half of the country in strong easterly winds".
That will continue into Thursday with predictions of "strong easterly winds and highs of just 1 to 4 degrees."
AA Roadwatch are warning motorists to take extra caution on the roads this morning.
Drivers are being reminded that it takes up to ten times longer to stop on an icy road.
In affected areas, slow down, keep further back from the vehicle in front and keep all manoeuvres gentle.
Pedestrians are also being asked to take care as paths and roads remain icy and slippery with a risk of black ice.
Dublin Fire Brigade are advising people to "walk like a penguin" - have a nice wide base, toes pointed outwards and take small steps - to wear sensible shoes and keep your hands out of your pockets so you can put them out in you fall.
According to Inner City Helping Homeless up to 80 people are still sleeping rough in Dublin despite the cold weather.
The charity's CEO, Anthony Flynn, has called on for emergency measures from Housing Minister Eoghan Murphy.
He said: "Although we've seen a 55% reduction in the number of people that are sleeping rough through the Christmas period and into January, we still have up to 80 people a night that are sleeping rough across the capital.
"We are urging with the Minister and pleading with the Minister to introduce contingency plans."
