Highest temperatures during the day will ‘widely exceed’ 25C and into the 30s in places, Met Éireann said.
An advisory for hot weather in the Republic of Ireland has been extended until Friday next week.
The Irish national weather agency said a “prolonged spell of very warm or hot weather” will continue this weekend lasting into next week.
Highest temperatures during the day will “widely exceed” 25C and into the 30s in places, along with a UV index of “high to very high”.
Met Éireann said warm and humid nights will occur, with overnight temperatures remaining above 15C, and a chance of thunderstorms on Wednesday and Thursday.
It warned of potential water safety issues due to increased use of waterways, lakes and beaches as well as uncomfortable sleeping conditions, heat stress and dehydration.
Met Éireann also raised concern over potential droughts and wildfires.
The advisory had been due to expire on Tuesday.
A status yellow high temperature warning also applies to 13 counties, with temperatures of 27C expected over the weekend – and uncomfortable nights.
It applies until 7am for Carlow, Kildare, Kilkenny, Laois, Longford, Meath, Offaly, Westmeath, Wexford, Cork, Limerick, Tipperary and Waterford.
The UK Met Office said temperatures could rise to 27C in Northern Ireland over the weekend.
