Many parts of the country have been affected by snow and ice overnight.
A status yellow warning from Met Eireann remains in place nationwide until 11am.
Very cold today, with a mix of bright or sunny spells & scattered showers, some of sleet & snow in the morning, but turning mainly to rain & sleet during the day with a risk of snow mainly over high ground. Maximum temperatures 3 to 6 Celsius in moderate to fresh westerly winds pic.twitter.com/Rcao0JediT— Met Éireann (@MetEireann) January 22, 2019
The worst of the snow is expected in Connacht, Ulster, north Leinster and on hills and mountains.
Drivers are being advised to slow down and take extra care on the roads with frost and icy patches in places.
Today is expected to be the coldest day of the week.
Met Éireann's Jean Byrne says it will stay cold for most of the day.
"We'll have maximum temperatures today only about 3-6 degrees. Quite breezy as well, especially in the first half of the day with fresh and gusty westerly winds."
It will be cold through much of this week with frost, icy patches and some wintry precipitation at times.
Temperatures are expected to increase Thursday into Friday, before turning colder again.
Met Éireann expects colder weather over the weekend, saying "current indications suggest it will becoming colder again this coming weekend, but still some uncertainty as to the exact detail as of yet."