The highest temperature recorded in Ireland on Monday was 26.6 degrees in Dublin's Phoenix Park at 3pm.
Met Éireann forecasters expect the same in Leinster on Tuesday, possibly reaching 27 degrees. Forecaster Matthew Martin said Tuesday looks like it would be "another good day", warm and mostly dry with temperatures ranging from 20 to 27 degrees.
Morning mist and drizzle will affect Munster and south Leinster Tuesday morning before being replaced with sunny spells. The best of the sunshine will be in parts of Ulster and north Leinster.
From Tuesday evening, conditions will turn more unsettled with showers spreading from the southeast, bringing the thundery downpours in the east and north.
Outbreaks of rain will push in off the Atlantic to affect the southwest and west. Lowest temperatures will fall back to around 14 to 17 degrees in mainly light to moderate southerly or southeasterly breezes.
The remainder of the week will be less warm and more unsettled.
Wednesday will be mostly cloudy with some sunny breaks while Thursday will see more rain with potentially heavy downpours over the western half of the country, bringing a risk of spot flooding.
The outlook for the weekend is for the mixed weather, with sunny spells and scattered showers, to continue.