Four counties have been hit with a Status Orange rainfall warning as "intense" thunderstorms are to hit.
Met Eireann has issued the rain alert for Longford, Cavan, Leitrim and Roscommon.
The national forecaster is predicting more than 50mm of rainfall and flooding for these counties throughout Monday afternoon.
The warning is valid from noon until 6pm on Monday.
A spokesman said: "Intense thundery downpours today, in excess of 50mm, will lead to surface flooding."
This alert is in addition to a thunderstorm warning currently in place for 21 counties.
Scattered thundery showers are set to lash most of the country on Monday afternoon, with the caution being valid until 9pm on Monday.
It will be in place for Cavan, Monaghan, Donegal, Carlow, Kildare, Kilkenny, Laois, Longford, Louth, Offaly, Westmeath, Meath, Galway, Leitrim, Roscommon, Sligo, Clare, Cork, Kerry, Limerick and Tipperary.
A similar warning has also been issued by the Met Office for Armagh, Fermanagh, Tyrone and Derry.
A Met Eireann spokesman said: "Scattered thunderstorms developing through the afternoon and evening with heavy downpours and a risk of localised flooding."
