The warning will be in place until Sunday morning.
A status yellow high temperature warning for 12 counties including the Midlands and Southeast is in place.
Laois, Offaly, Westmeath, Longford, Meath, Carlow, Kildare, Kilkenny, Wexford, Cork, Limerick, Tipperary and Waterford are impacted.
The warning is in place until 7am on Sunday with highs of around 27 degrees, while it won't fall below 15 degrees at night.
People are being advised to exercise caution around lakes, rivers and beaches.
Moate's Brian Smyth, CEO of Irish Rural Link, is urging people to check in on older and vulnerable neighbours during the current heatwave:
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