The advisory comes into effect from midday today and is valid until midday on Friday.
Temperatures reached 29.5 degrees in Athenry, Co Galway yesterday, making it the hottest day of the year so far.
Alan O'Reilly from Carlow Weather says today will be another warm day:
"It would be very warm again we're just that small sleet sea breeze on the course, making that a little bit cooler, but really it is warm right across the country and very humid as well, with some very warm nights, obviously."
