A Status Orange warning for rain is in place for four counties in Leinster, with Met Éireann warning of widespread surface flooding and “hazardous” travel conditions.
The warning for counties Dublin, Wicklow, Louth and Meath, is in place until 2pm.
Persistent and heavy rain is forecast, with a chance of thunderstorms, leading to “very difficult and hazardous” travel conditions and “very poor” visibility in many areas.
A Status Yellow warning for rain is also in place until 2pm for counties Kildare and Monaghan, where Met Éireann has said localised flooding is possible.
Elsewhere will be drier with isolated showers as the day goes on.
Later in the afternoon, rain in the east will ease and become patchy, with Met Éireann forecasting highs of 15-20C.
Meanwhile, the UK Met Office has an Amber warning in place for counties Antrim, Armagh and Down until 8am, which will revert to a Yellow warning thereafter until 2pm.
Very heavy rainfall was expected through the night into this morning, with the potential for flooding.
The PSNI is advising road users that the Marble Arch Road, Florencecourt and Sligo Road in Enniskillen are all impassable due to floods.
Flooding was also reported to have been affecting other parts of west Fermanagh.
