Met Éireann has issued a weather warning for heavy rain and thunderstorms for much of the country.
The status yellow warning is for all of Leinster and Connacht, and counties Cavan, Donegal, Monaghan, Connacht, Tipperary and Waterford.
The heaviest rain is likely to be in Ulster counties and the midlands. Showers will give away to prolonged periods of rain in the late afternoon.
There is a possibility of heavy, potentially thundery downpours breaking out this afternoon and evening, producing some localised flooding.
The warning is valid until 9pm on Thursday night.
The UK Met Office has issued a similar weather warning for Northern Ireland with heavy showers and thunderstorms having the potential to bring surface water flooding in parts and disrupt travel.
The thunderstorms are likely to bring an end to the Indian summer the country has seen, with temperatures reaching as high as 26 degrees in parts in recent days.
Friday will see a return to more normal conditions for this time of year and it will feel notably cooler and a little fresher over the weekend and into next week.
