Temperatures are expected to climb to 25 degrees on Thursday with the hottest temperatures set to be on the west coast.
Met Éireann said it will be mostly sunny and dry, with any mist clearing during the morning.
Cloud will build at times across parts of Ulster and Connacht. High temperatures will range from 19 to 25 degrees. A light easterly breeze will keep it a little cooler along eastern coasts.
Met Éireann meteorologist Liz Walsh said it looks as though Shannon Airport and west Galway will be the hottest spots. “Yesterday it was Mace Head and Connemara, and there is a station in Co Clare that went over 25 degrees,” she said. “I would expect similar today.
“There is a bit of mist around and flat cloud. That is affecting parts of north Leinster and eastern Ulster, and that is expected to break up.
“We might see more cloud developing further west later. It should brighten up in Dublin. There will be very sunny conditions in southern areas.”
Ms Walsh also warned people to be “sun smart” and to take care around water spots.
“UV levels are high and the air is very clean over Ireland,” she said. “That means the sun can get through and can be quite strong. So the advice is to be sun smart, and also be careful if you are out on the water.
“A lot of people tend to get out there when the weather is fine and people need to take the proper precautions. The winds can pick up. There is a small craft warning off Connacht today where it could get choppy. Even in the fine weather, winds can pick up at sea.
“The wind looks like it will pick up later today, so plan and prepare if you are going outdoors.”
Later on Thursday night, it is expected to be dry and clear apart from a few isolated fog patches. The lowest temperatures will range from 7 to 12 degrees in light easterly or variable breezes.
The hot weather is expected to continue for the rest of the week, with the forecaster predicting it will be warm and sunny on Friday outside of some possible cloud building across Ulster.
There will be high temperatures of 18 to 24 or 25 degrees, all the while a little cooler though along Irish Sea coasts. Winds will be light to moderate northeast or variable.
Another largely sunny and dry day is expected on Saturday with just scattered cloud. It will be somewhat cloudy to begin in northern parts, clearing in the afternoon.
The highest temperatures that day will range from 18 to 23 degrees, with just light easterly or variable winds.
It will remain dry and clear overnight on Saturday with just the odd patch of mist developing before dawn. Temperatures will not fall below 8 to 11 degrees, and there will be light easterly or variable winds.
A clear sunny start is forecast for Sunday with variable cloud possibly developing over the western half of the country later on in the day, before clearing again in the late evening.
The highest temperatures that day will range from 18 to 25 degrees with just light easterly or variable winds.