Rain has returned to the capital following weeks of drought.
Dublin's skies were grey for most of yesterday, though temperatures reached a maximum of 21C.
Travel agency Sunway said it had seen "a 20pc increase in bookings and enquiries both online and through our call centre" due to the break in the good weather.
The cooler temperatures, rain showers and grey spells across parts of the country had only "proved how unpredictable our Irish climate is", said Sunway managing director Tanya Airey.
Meanwhile, the heatwave has led to the discovery of possible archaeological sites near the Unesco World Heritage location close to Newgrange in Co Meath.
The Department of Culture and Heritage said a "very significant find" had been spotted and photos showed a henge or circular enclosure structure that had become visible in a field at Bru na Boinne.
The henge measures up to 200 metres in diameter and may have been built around 500 years ago, long after Newgrange.
The temperature is expected to peak at 25C today in the south of the country, with only isolated showers to offer a little reprieve as drought conditions remain.
There will be isolated showers this afternoon.
Temperatures in Dublin will peak at 20C or 21C and there will be light breezes.
Met Eireann meteorologist Joan Blackburn said the weather will remain "really very pleasant", and although there will be a little rainfall also expected in Ulster, the drought weather warning remains in place.
The highest temperature yes- terday was at Moore Park weather station in Munster at 25C, while Valentia reached 24.5C.
Those hoping for the heatwave to continue may be a little disappointed, as temperatures could drop tonight.
"Friday will see a lot of dry weather and Saturday and Sunday will see the odd shower but there will be no major rainfall," Ms Blackburn said.
"There will only be scattered showers, and temperatures will remain in the high teens and low 20s across the country."