Met Éireann has issued a Status Yellow rain and thunderstorm warning for four counties in the west and south, and a separate thunderstorm warning for a further ten counties mostly in the east.
The rain and thunderstorm warning covers counties Clare, Kerry, Limerick and Galway.
The Status Yellow thunderstorm warning has also been issued for Carlow, Dublin, Kildare, Kilkenny, Laois, Louth, Meath, Offaly, Westmeath and Wicklow.
The forecaster said that all affected counties may experience lightning damage.
Counties Clare, Kerry, Limerick and Galway may see downpours which cause surface water flooding and make travel difficult.
The warning covering those counties is valid from 7pm today until 7am tomorrow.
The warning covering the ten mostly eastern counties came into effect at 12:25pm and expires at 4pm.
Temperatures today will rise to 15C in some areas, reaching 21C in others, Met Éireann has forecast.
Rainfall will continue into the night, with lowest temperatures of 9C to 13C.
The outlook for the rest of the week is “[mixed] and changeable overall”, with weather being “[cooler] and fresher than recently, but turning a little milder around mid-week”.
