A status orange thunderstorm warning has been issued for the entire country.
It is an upgrade from the previous yellow warning - with heavy showers of rain combining with high temperatures.
The orange thunderstorm warning begins at 3pm today until 9am tomorrow for most parts, but continues for South Leinster and Munster until 4pm tomorrow.
That's on top of an existing yellow heat warning which is in place for Leinster, Munster, Cavan, Monaghan, Galway and Roscommon until 6am tomorrow.
Met Eireann's Andrew Doran Sherlock says the thunderstorms will hit quite sporadically so not everywhere will get hit:
"Every area is at risk, but not everywhere will see it because they can be quite localised developments. So a one kilometre difference could dictate whether you are experiencing the heavy thunderstorm or not - but all areas are at risk."