Met Éireann has extended the current status orange thunderstorm warning until 10pm on Monday 15 August.
The warning has been in place since Sunday at 3pm and was due to last until 3am Monday morning, affecting all 26 counties.
It has now been extended to Monday night, with 14 counties set to bear the worst of the adverse conditions.
Met Éireann has said that this thunderstorm activity is expected to persist particularly in Munster and Leinster.
The counties affected are Carlow, Clare, Cork, Dublin, Kerry, Kildare, Kilkenny, Laois, Limerick, Offaly, Tipperary, Waterford, Wexford, and Wicklow.
Due to the sporadic nature of development, not all areas will be affected, Met Éireann has said.
Heavy downpours of rain and hail will occur in places and flooding is likely where these downpours occur.
"The thunderstorms will become more intense later this afternoon and evening," Met Éireann has said.
Meanwhile, temperatures this afternoon will return closer to average, ranging from 15°C to 17°C in the north and west, and between 18°C and 23°C elsewhere.
Light to moderate northerly winds will increase fresh to strong along Atlantic coasts.
Showers will gradually die out in the south to leave a mostly dry night, with clear spells.
Lowest temperatures of 10°C to 14°C, remaining warmest near the east coast.
Moderate northerly breezes will be fresh at times near northward-facing coasts.