Temperatures are to fall back to -1 in some places
Met Éireann is forecasting much colder weather for the later part of this week.
While temperatures for Monday, Tuesday and Wednesday will stay around 7 to 11 degrees, change is coming from Wednesday night.
The forecaster says there will be "a noticeable change" as very cold air moves in from the northwest.
Scattered showers will become increasingly wintry with sleet or snow likely - mainly in parts of Ulster and Connacht.
Frost will also develop in many areas also.
Lowest temperatures of between -1 to +1 are forecast.
It says Thursday will be "a bitterly cold day", with temperatures only rising to between 3 and 6 degrees in moderate to fresh westerly winds.
There will also be a mix of sunny spells and scattered wintry showers, most frequent over the western half of the country.
The highest risk of snow will be in the morning and during the evening and night.
Friday will continue to be very cold with sunny spells and further showers of rain, sleet and snow.
Temperatures will again reach between 3 and 6 degrees with westerly breezes.
While there will also be a sharp frost on Friday night.
The weekend will continue very cold with further showers of rain, sleet or snow and with sharp or severe frosts at night.
It comes as the deaths of eight people in Italy have been blamed on freezing weather, as blizzards and dangerously cold conditions continue across Europe.
One man died in the basement of an unused building in Milan, while another passed away on a street flanking Florence's Arno River.
As snow fell in Istanbul, Turkish Airlines was forced to ground hundreds of flights for the third day running.
A dozen major roads remained closed in Romania, again because of snowfall, while some ferry services between Romania and Bulgaria across the River Danube were cancelled.
Authorities said schools would be closed in many areas on Monday and Tuesday, including the capital, Bucharest.
Police in Bulgaria said a passenger train derailed on Sunday after it hit a pile of snow in the central area of the country.
Four Portuguese nationals were killed when a bus skidded on an icy road in eastern France early on Sunday.
Black ice across northern and western Germany has caused a number of accidents and injuries.
Firefighters in the city of Hamburg said they had been called to weather-related accidents 415 times over the weekend.
One person died in a car accident near Hannover when his car skidded against a tree on an icy road, German news agency DPA reported.
City authorities shut down the public transport system, while across the country people were told to stay at home until the severe weather eased.
Additional reporting: IRN