Children play in a water installation on the South Bank today, as temperatures reached 33C — the hottest August day in a decade.
Following a scorching July, the heatwave had this week begun to face, but it made a one-day reappearance.
Tomorrow will be cloudier with some showers in the morning.
The weekend will see temperatures return to an average 23C.
The new wave of warm weather comes after some parts of the country experienced the hottest July on record.
Forecasters said temperatures in the west, Dublin, the south west and midlands were at their highest for up to 63 years.
In Kerry, Valentia Observatory average temperatures matched a 1921 record, which is the highest since it began taking records 120 years ago.
Other weather stations around the country reported the warmest July for seven to 30 years.
Met Eireann said nine areas where it records conditions experienced heatwaves - technically five days or more of temperatures over 25C (77F).
The mercury rose highest during July in Ardfert, Co Kerry, where it reached 30.3C (87F) on July 19.
As a result of the long, hot spell, most parts of the country were also hit with droughts.
Thunderstorms towards the end of the month made up most of the rainfall for July.
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