Met Éireann has issued a status Yellow Weather Alert, warning of heavy rain and strong winds in parts of the west and northwest.
A wind warning for Sligo, Donegal, Galway and Mayo will take effect from midnight on Christmas Eve until 8pm.
Heavy rain is forecast from 9am on Christmas Eve to 9am on Christmas Day in counties Sligo, Donegal, Leitrim and Mayo. Local spot flooding is also expected.
Met Éireann has also issued a weather warning for Christmas Day in Munster and Leinster.
It said that rain is likely to become persistent and heavy throughout the day.
Meanwhile across the country Met Eireann say the change to the more unsettled period of weather from Christmas Eve onwards with the risk of frost and ice returning, some heavy rain and the threat of wintry precipitation also.Sunday night/Christmas Eve
Wet and windy, as a band of heavy and persistent rain in the north and west gradually spreads southeastwards overnight. The rain will ease or die out over much of Connacht and Ulster by dawn. Fresh and gusty southwesterly winds will veer westerly with the clearance of the rain and ease. Lows of 4 to 8 degrees Celsius, with the coldest temperatures occurring in the north and west towards morning.
Christmas Day will be a wet day in many parts, with further heavy rain in places. Cooler, drier and eventually clearer conditions with showers will slowly edge into western areas during the afternoon, but the mostly cloudy and wet conditions will likely persist further east. Turning a lot colder towards evening with a risk of sleet and hill snow as the rain clears eastwards. Afternoon highs of 4 to 7 degrees, but 8 to 10 degrees in the far southeast. Cold and frosty overnight with clear spells and scattered showers, a few of them heavy with hail and with wintry falls over high ground, these chiefly confined to Atlantic coastal counties. Lows of -1 to plus 2 degrees Celsius, with a risk of ice on untreated surfaces, despite the moderate to fresh west to southwest winds.
Tuesday/St. Stephens Day:
A cold day in store. A bright start, with frost clearing. But cloud will soon increase in the southwest as a band of heavy rain pushes in off the Atlantic. There is a risk of sleet and hill snow on the leading edge of this band of rain, but still a good deal of uncertainty on the northern extent of the rain with Munster and south Leinster the main areas of concern at this stage. A few wintry showers will affect the northwest coasts also. Highs of just 3 to 6 degrees Celsius generally, but locally up to 8 Celsius along the south coast. Further rain, sleet and some snow showers are possible overnight, but dry clear spells developing too. Lows of minus 2 to plus 2 degrees Celsius, with a widespread frost and the risk of ice on untreated surfaces.Wednesday:
Early frosts clearing, with showers becoming increasingly confined to northern coasts, leaving crisp cold sunny spells for many parts. Afternoon highs in the low single figures. Cold overnight, with clear spells and icy conditions on untreated surfaces. Minima dipping below freezing in many places.Further outlook:
Continuing cold, changeable and unsettled.