Met Éireann has warned of hazardous travel conditions as Storm Chandra is forecast to bring very strong winds and heavy rain across the country.
The forecaster said persistent rain will fall on already saturated ground, leading to a risk of localised and river flooding.
A Status Yellow rain warning is in effect for counties Carlow, Kilkenny, Louth, Wexford, Wicklow and Waterford until 11pm.
The entire country also remains under a Status Yellow wind warning until the same time as Storm Chandra passes over the country.
The possible impacts of strong gusts, Met Éireann warned, could include fallen trees, loose debris and wave overtoppping.
The UK Met Office issued an Amber wind warning for counties Antrim, Derry and Down, with the remaining counties in Northern Ireland under a Yellow level warning.
The Amber alert is valid from 5am until 9pm, while the Yellow alert is in effect until around midnight.
The UK Met Office said gusts of 60-70mph will affect eastern Northern Ireland, with possible 75mph gusts in coastal locations, adding that "easterly winds of this strength are unusual and are likely to be impactful".
A Status Orange marine warning will also come into effect for coastal areas in the south from 9am until 4pm.
With rain falling on already saturated ground and many rivers already at high levels, there is a significant risk of flooding over the coming hours.
The River Slaney in Enniscorthy, Co Wexford, is of particular concern with Wexford County Council saying its crews remain on standby to provide assistance if required.
Conditions are expected to worsen from lunchtime onwards based on the low pressure, winds and rainfall forecasted.
Storm Chandra is the next storm to be named by the western Europe storm naming group list shared between Ireland, the UK and the Netherlands.
It is the third named story of the year and means Hindu god of the moon.
