The forecaster said it will be very warm or hot on Thursday, Friday and Saturday with maximum temperatures generally between 27C to 29C.
The warning, which covers all of Leinster and Munster, is valid from 12pm on Thursday until 6am on Sunday.
The forecaster said it will be very warm or hot on Thursday, Friday and Saturday with maximum temperatures generally between 27 to 29 degrees.
It will be warm at night with temperatures generally staying above 15 degrees, although daytime temperatures may not be as high in coastal areas due to sea breezes.
Met Éireann has warned that this may result in heat stress, especially for the more vulnerable of the population.
There is also a high solar UV index and an increased risk of water related incidents as people flock to the water to cool down.
There is also a weather advisory in place as the county will experience a hot spell developing from today and continuing through the rest of the week and the weekend.
Daytime temperatures will widely reach the mid to high 20s and it will remain uncomfortably warm overnight too.
This comes as today will be another dry, warm and sunny day with highest temperatures between 24 to 26 degrees, higher in some spots in Munster and Leinster.
Winds will be light variable or calm with a sea breeze developing in the afternoon. A moderate southwest wind will keep it cooler on the coast of Connacht and the west coast of Ulster.
Tonight will be dry and clear with lowest temperatures between eight to 13 degrees with no wind.
Met Éireann forecasts that high pressure will dominate the weather picture and each day will be dry, warm and sunny with light winds.
Sea breezes will form in the afternoons for a couple of hours and nights will be dry and clear.
Thursday will be dry, warm, sunny and hot in Munster and Leinster with highest temperatures between 24 to 28 degrees. There will be sea breezes again in the afternoon and it will still be cooler along the coasts of Connacht and west Ulster.
It will be warm overnight with temperatures not falling below 10 to 15 degrees generally, staying above 16 or 17 degrees in places.
It will continue dry and clear with some coastal fog forming along Connacht and west Ulster coasts with light variable breezes.
Friday and Saturday will be hot and sunny with a low chance of isolated showers.
Highest temperatures will range between 25 to 28 or 29 degrees in light variable breezes, hottest inland.
It will stay warm overnight with temperatures not falling below the mid to high teens.
It will be another hot day on Sunday with sunshine to start, there's an increased likelihood of showers, and they could be heavy with highest temperatures between 25C to 29C with light easterly breezes.