A low temperature of almost minus 6 degrees was recorded overnight.
The weather station in Gurteen in Co Tipperary recorded the coldest temperature overnight of minus 5.7 degrees.
A low of minus 4.9 degrees was recorded in Mullingar in Co Westmeath, while Claremorris in Co Mayo and Casement Aerodrome in Dublin recorded lows of minus 4.
Hazardous conditions are being reported across the country this morning and schools will remain closed in many parts, while transport services also face disruption.
An orange advisory for low temperatures and ice is in place for 22 counties until 10am this morning, while another orange alert will kick in at 6pm this evening.
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