Status Orange weather warning: Freezing temperatures for most of the country
Met Éireann has issued a Status Orange low temperature warning for this evening, with severe frost and temperatures reaching as low as minus 6C in certain counties.
The warning is in place for Munster, Inland areas of Leinster, Connacht, Donegal, Monaghan and Cavan, with bitterly cold lows of between minus 4C and minus 6C.
The warning will be in effect from 9pm Sunday until 10am Monday, making for a possibly hazardous first school run of the year.
Last night, temperatures were plunged to a winter low of minus 5C in some areas, and the cold snap will stay until the middle of the week.
Met Eireann warned of widespread frost, icy patches and freezing fog all weekend.
Today will be dry and sunny but very cold, with temperatures reaching no more than 2-5C.
Winds will be light today, but temperatures will have "a little struggle to get above freezing" during daylight hours.
Frost will become widespread again tonight, with icy patches and freezing fog in places.
Connacht and Ulster are set to be coldest.
Tomorrow it will become cloudy over Munster and Leinster, with isolated patches of rain, though the day will be mostly dry.
It will also be dry with sunny spells across Connacht and Ulster. But it will be another cold day, with highs of 4-8C in freshening south-easterly winds.
Temperatures will remain low until Thursday, when milder conditions are forecast to finally return.
Meanwhile, motorists are being advised to check the condition of their car, as parents prepare to drive children back to school at the end of the Christmas holidays.
AA Rescue said tomorrow could be a particularly busy day for breakdowns.
Parents are being advised to start and run their car for a few minutes today - particularly if it has been idle for a significant period over Christmas.
This will ensure the battery is functioning. They should also carry out basic checks, especially on lights.