Status Yellow snow and ice warnings are in place in 11 counties in the north and northeast.
The counties covered by the warning issued by Met Éireann include counties Cavan, Donegal, Monaghan, Leitrim and Sligo.
The warning began at midnight and will last until midday tomorrow.
A separate Status Yellow snow and ice warning has also been issued by the UK Met Office across all counties in Northern Ireland until midday.
Wintry showers of hail, sleet and snow are forecast, with modest snow accumulations expected in places, especially on high ground.
Met Éireann has warned of hazardous travelling conditions and icy stretches as possible impacts.
The general forecast for Ireland is that it will be cold with sunshine and scattered showers, some of the showers will be wintry with hail and sleet.
Some snow showers are possible too, mainly over higher ground in the north and northwest.
Although temperatures will be around 3C to 7C, it will feel even colder with an added wind chill factor from moderate to fresh north to northwest winds.
Frost and ice will become widespread for a couple of nights, with temperatures dropping to as low as -3C in some areas.
Met Éireann meteorologist Rebecca Cantwell warned earlier this week that people should wrap up and give themselves extra time in the morning to defrost their cars.
However, by Friday, there should be a return to milder Atlantic air, she said.
