December was officially the coldest on record as Arctic conditions left a blanket of frost and heavy snowfall across the country.
The picturesque white Christmas saw temperatures plummet to the lowest on record, with minus 17.5 degrees in Straide, Co Mayo.
In the Dublin area the temperature on Christmas Day fell to minus 15.7 degrees - the coldest since data began over 50 years ago.
Met Eireann's monthly weather summary showed that by December 25 there was 27cm of snow lying at Casement Aerodrome.
Forecasters warn the cold spell is set to continue with temperatures due to fall to minus four degrees on Wednesday night, followed by up to 10cm of snow in many areas by Friday.
The summary said spells of exceptionally cold weather during the month brought some of the lowest temperatures ever recorded in Ireland.
Around the country between 14 and 24 days with air frost were recorded during the month, more than twice the normal number for December. But there were also short periods of milder weather making the month was drier and sunnier than normal.
"Mean air temperatures for the month were up to six degrees lower than normal in places and it was the coldest December on record almost everywhere," it added.
Elsewhere monthly rainfall totals were below normal everywhere but sunshine totals varied widely, with both Belmullet and Valentia Observatory recording their sunniest December on record.
Met Eireann said while 2010 began and ended with spells of exceptionally cold weather, the months between April and September were warmer than normal with total rainfall below normal.