A Status Yellow warning has been issued for parts of the east coast for Wednesday afternoon.
Temperatures of up to 28C are forecast for parts of counties Dublin, Carlow, Kildare, Wicklow and Meath.
The warning will be in effect from midday until 6pm on Wednesday evening.
The country has enjoyed temperatures in the 20s since the weekend, but that is forecast to come to an end from Thursday when it will become noticeably cooler.
Temperatures from Thursday into the weekend are forecast to be in the mid-to-high teens.