There is a flood risk in 17 counties as heavy rain is due to fall on already saturated ground.
On Tuesday morning, Met Éireann issued a yellow warning for rain applying to all of Leinster as well as Cavan, Monaghan, Cork, Tipperary and Waterford.
The warning will be in effect between 11pm on Tuesday and 11pm on Wednesday.
It is a significant expansion of the advisory, which was first announced on Monday.
Weather bosses said there is a risk of flooding, poor visibility and difficult travelling conditions in these areas, which are also experiencing high river levels.
The inclement conditions will be exacerbated by strong and gusty south-easterly winds in five of these counties.
Wexford, Wicklow, Meath, Louth and Dublin will also be under a yellow warning for wind, with Met Éireann also cautioning against wave overtopping amid high tides.
The wind warning is between 11pm on Tuesday and 1pm on Wednesday.
The double warning applies to areas in the east of the country which have been severely affected by flooding in recent weeks.
Meanwhile, Met Éireann has said that Atlantic low pressure will continue to dominate, with Status Yellow snow warning for three counties as temperatures drop below freezing.
People woke up to a cold Tuesday morning all over Ireland, with frost and ice making roads and pathways difficult to travel on.
Some counties recorded temperatures as low as -4C, though the southwest was slightly cooler than the rest of the country.
Snow warning for three counties as ‘Atlantic low pressure remaining dominant’
A Yellow snow warning will be introduced at 2am on Wednesday morning for Donegal, Leitrim and Sligo, lasting until 2pm later that day.
Met Éireann has warned that heavy rain could turn to sleet and snow, leading to poor visibility and difficult travelling conditions.
