The warm weather looks set to continue, with temperatures as high as 22 degrees Celsius forecast on Monday.
While highs of 20 degrees Celsius were reported on Sunday, Met Éireann predicts temperatures will rise even higher on Monday.
However, the forecaster also said Ireland can expect fresher weather by midweek.
Met Éireann said Monday will be humid, with sunny spells in Ulster and Connacht and temperatures of between 19 and 22 degrees Celsius.
These temperatures will lead to thundery showers in some places.
Hazy sunshine is forecast on Tuesday, with temperatures of between 18 and 20 degrees Celsius.
However, Tuesday will also see rain and showers in places, especially in Munster and Leinster.
These showers will extend across the country on Wednesday, as temperatures drop to between 14 and 18 degrees Celsius.
Forecaster John Eagleton said the best days would be next Monday and Tuesday before conditions settle.
“The charts are showing us it will reach 21 degrees and 22 degrees. It may not be as high in Dublin because the winds will be easterly, but certainly in the midlands and the west of the country, that is what we are forecasting.”
“Maybe we are getting an Irish heatwave,” he joked. “The Italians would laugh at it, but we’ll take whatever we can get.”
Cold April
May’s high temperatures follow on from the coldest and dullest April in decades.
A recent Met Éireann report showed it was the coldest April in Dublin in 16 to 30 years, with mean temperatures between 1 to 1.5 degrees Celsius below average.
Mr Eagleton said it had been a late spring but that the current weather “will make up for it now - there will be a real burst of growth”.
Official figures released by Met Éireann showed temperatures dropped as low as -3 degrees Celsius in Sligo last month.
Dublin recorded its coldest April in 27 years - with ground frost recorded in the capital on 23 days of the month.
The city also endured its dullest April since 1998, according to records from the weather station at Casement Aerodrome.
Cork Airport recorded the wettest April day since 1978 on April 10th.
Additional reporting: PA