Met Éireann has said that overnight temperatures from this Thursday will reach "uncomfortably warm" levels, as the country is set to experience temperatures above 25C from Wednesday for up to five days.
The forecaster has issued a weather advisory, saying that a hot spell will see daytime temperatures reach the mid-to-high 20s from Wednesday through to the weekend.
The advisory, valid until next Monday, states that temperatures will remain uncomfortably warm overnight - reaching 14C - and highlights the potential risk of heat stress among vulnerable people throughout this week, as well as the risk of water-related incidents.
Met Éireann meteorologist Joanna Donnelly said that high pressure has built since last weekend, leading to "blue skies, hot" conditions from the middle of this week.
"It's settling over the country. The sun is heating us up directly. It is August so the sun is not as high as it was in June, but it's still high enough," Ms Donnelly said.
Speaking on RTÉ's Today with Philip Boucher-Hayes, she added: "Every day is going to get a little bit warmer. We've got that going since Friday and it will stay with us right through this week.
"From Wednesday we've got even warmer air. It's going to be blue skies, hot.
"After Thursday things might get a little bit uncomfortable. Overnight temperatures will be about 13C or 14C."
Earlier, Met Éireann forecaster Conall Ruth said that all parts of the country can expect to see the mercury climb into the 20s over the weekend.
"There is still a bit of uncertainty, but generally we can expect widespread temperatures in the mid-20s later in the week from around Wednesday onwards and possibly getting up into the high-20s in some parts by Friday, and the hottest temperatures are currently expected to persist right the way through the weekend," he said.
Speaking on RTÉ's Morning Ireland, Mr Ruth added: "The nights will also be a good bit warmer than average, especially from around Thursday night onwards, with temperatures not really falling below the mid-teens.
"Generally the southeast of the country is expected to see the highest temperatures over the coming days, but the midlands will then also get very hot as we head through the weekend and it will stay coolest near western and northwestern coasts, but based on current projections all areas can expect to see temperatures reach at least the low-20s over the weekend."
Temperatures are expected to hit as high as 28C on Friday, with 26C and 27C forecast for Wednesday and Thursday respectively.
The hot spell comes as countries across Europe deal with rolling heatwaves over the summer months.
France is braced for a fourth heatwave this summer as its worst drought on record left villages without safe drinking water and farmers warned of a looming milk shortage in the winter.
In Italy, the drought-stricken waters of the River Po are running so low they revealed a previously submerged World War II bomb.
Faced with a historic drought and threatened by desertification, Spain is rethinking how it spends its water resources, which are used mainly to irrigate crops.
Like France and Italy, Spain has been gripped by several extreme heatwaves this summer after an unusually dry winter.
Scientists warn that current heatwaves have been made hotter, longer and more frequent by climate change.