Snow and ice weather warnings have been issued for most parts of the country.
The most severe is a status Orange snow and ice warning for 11 counties: Carlow, Kildare, Kilkenny, Laois, Longford, Wicklow, Offaly, Westmeath, Galway, Roscommon and Tipperary.
Also, a yellow snow and ice warning is in place for Wexford, Clare, Kerry, Limerick and Waterford.
Both warnings are in place until late tonight.
Forecasters are expecting extremely low temperatures across the whole country from 8pm tonight with severe frost, ice and lying snow.
They say that the lowest temperatures will be -2 to -8 degrees Celsius, with the coldest in east Connacht, Leinster and Ulster.
Freezing conditions are expected to spread southwards across the afternoon.
Liz Walsh, a forecaster in Met Eireann, says there is a big variance in temperatures across the country.
She said: "There is a nine degrees recording at Sherkin Island and at a buoy in Co. Galway it is just zero degrees. In between that area there is a front lying across the country which is slowly starting to sink southwards.
"There is rain, snow and sleet in that front and as that front sinks southwards it is going to draw the cold air behind it with it and we can expect, as we go through this afternoon places that are at six or seven degrees right now will actually decrease in temperatures."
An Orange weather Warning remains in place for 13 counties across the country this morning.
Met Eireann is warning of icy conditions and snow accumulations of between four and eight centimeters.
They include: Cavan, Monaghan, Donegal, Dublin, Kildare, Laois, Longford, Louth, Wicklow, Offaly, Westmeath and Meath.
This warning is valid until 11pm tomorrow night.
There is also a Yellow snow and ice warning affecting five counties, including Dublin, Waterford and parts of Ulster and Connacht.
The forecaster has also issued Yellow wind and rain warnings.
Evelyn Cusack forecaster with Met Eireann says it is a real mixed bag across the country.
She said: "We have windsup to storm force along the south coast, heavy rain up over parts of Munster and southern parts of Leinster.
"And then after this heavy rain has met the very cold air to the north, we've got a mixture of rain, sleet and snow across Connacht and Leinster, and Ulster is actually clear and frosty, so you have all types of weather.
"The rain, sleet and snow will continue through the morning and into the afternoon, causing some dangerous conditions in places."
Meanwhile, Gardaí have issued a road safety notice for people living in counties affected by the Orange weather warning.
They are warning against unnecessary travel in the affected areas, and are urging the public to heed the changing conditions before travelling.
They are reminding drivers that it takes longer to stop a vehicle on an icy road and asking drivers slow down and to keep a safe distance to the car in front.
Motorists are also being advised to ensure that all ice is cleared from windscreens, windows and mirrors of vehicles before taking to the road, and are being asked not to use hot water.
Gardaí also say that any snow must be cleared from the roof of the car, as it can fall onto the windscreen while braking, potentially causing restricted vision.
Assistant Commissioner Michael Finn is also urging motorcyclists and cyclists to not compromise their safety by the "need" to travel in snowy or icy conditions.