Sub-zero overnight temperatures can be expected this week, as a yellow snow-ice warning takes effect.
It will be in place for five days and temperatures will drop.
Met Éireann says there will be widespread frost at night with icy stretches on untreated surfaces.
Wintry showers will be frequent across the southwest, west and north.
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. Otherwise, we'll just get some wintery showers later on today and tonight and both of those will be in the western half of the county."
Met Éireann says that tonight will see a chance of snow with temperatures falling to around 0 degrees while Wednesday night 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."
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."
