Met Éireann has issued a yellow warning for high temperatures for 14 counties on Friday and for the rest of the country on Saturday.
Conditions are set to become “very warm or even hot” in the coming days with temperatures possibly breaching 28 degrees this weekend, said Met Éireann. Night-time temperatures are also expected to be in excess of 15 degrees.
Friday’s warning applies to counties Carlow, Dublin, Kildare, Kilkenny, Laois, Longford, Louth, Meath, Offaly, Westmeath, Cavan, Monaghan, Roscommon and Tipperary.
Following an already warm and humid start to the week, with a peak of 25.5 degrees on Wednesday at Phoenix Park in Dublin, high pressure which has settled over Ireland will see temperatures rise further from Thursday.
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Alongside mainly dry and settled conditions, the forecaster expects “very warm or even hot” days ahead.
Thursday was to be a “very warm” day with highest temperatures ranging from 22 to 27 degrees.
Clear skies are likely to develop on Friday “becoming hot in sunshine” with highs of 22 to 28 degrees expected, though a representative for Met Éireann said temperatures could go above 28 degrees throughout the weekend.

Saturday is set to be another “very warm or hot day”, with the eastern half of the country likely to experience the best of the sunshine while more cloud is expected further west.
Sunday will start off dry with sunshine in the east and north but cloud and showery rain is expected to move in over Munster and Connacht in the afternoon before gradually extending north-eastward throughout the evening and night.
Despite this, similar highs of 22 to 28 degrees are expected on Sunday.
Met Éireann says current indications suggest a “cooler and more unsettled” start to next week.
Showers and longer spells of rain are expected early next week with temperatures, as of now, forecast to be in the high teens to low 20s.
As the UV index is set to remain high to very high over the coming days, the HSE recommends using SPF, hats and clothing to protect the skin from harsh ultraviolet levels.
It also advises seeking shade or avoiding being outside entirely during midday hours while UV levels are eight and above.
Before an expected influx to rivers, lakes and beaches over the coming days, meanwhile, Water Safety Ireland has urged the public to “stay alert” and to choose swimming areas where lifeguards are present.
It also warned prospective swimmers to watch their step in shallow sandy waters where weever fish lie buried along the Irish coast.
“If accidentally stepped on, their dark-tipped spines can deliver a painful sting. To reduce the risk, wear beach shoes when paddling or walking in shallow water. If stung, immerse the affected area in hot water which helps break down the venom’s protein,” it said.
These cautions come alongside a national appeal from Uisce Éireann to conserve water amid already increasing pressure on the water network.