Met Éireann has issued a status yellow high-temperature warning for 18 counties starting from Thursday as it forecasts highs of 29C.
The warning is currently in place from 12pm on Thursday until 6am on Sunday morning for all counties in Leinster and Munster.
It comes as the hottest place in the country today was recorded at Moore Park weather station in Cork which saw temperatures hit 27C.
Carlow saw highs of 26C while Tipperary recorded 25C and parts of Dublin, Westmeath, Meath, Roscommon and Limerick reached 24C.
Ireland will see temperatures nudge 30C over the next few days as a heatwave grips the country.
"Very warm or hot on Thursday, Friday and Saturday with maximum temperatures generally of 27 to 29C,” Met Éireann said today.
"Warm at night with temperatures generally staying above 15C. Daytime temperatures may not be as high in coastal areas due to sea breezes.”
The forecaster said a heatwave consists of temperatures above 25C in the same location for five consecutive days.
It added that the impacts this hot weather will have is heat stress, especially for the more vulnerable of the population, a high Solar UV index and a risk of water related incidents.
The charity ALONE has expressed concern for older people as temperatures are expected to spike and urged members of the public to check in on elderly neighbours, friends and relatives this week.
The organisation which supports older people, is advising older people to keep cool and hydrated over the coming days and to take regular breaks from the sun.
Temperatures are currently above average for the month of August.
Speaking earlier today, Meteorologist Paul Downes said the hot spell in July was a “short, sharp burst”, however, this time it is more prolonged, and it is going to be quite warm and muggy overnight.
He said some areas along the east coast could experience temperatures in the high teens overnight making for quite uncomfortable sleeping conditions.
Mr Downes said the highest temperature recorded in August was 31.5C and it is “unlikely” that it will be surpassed but temperatures could reach 30C towards the end of the week.
He said temperatures went a little bit above Met Éireann’s forecast model suggestions on Monday. He said Saturday currently looks to be the hottest day of the week so far.
Temperatures will widely reach 25C across the country tomorrow with highs of 27C possible.
Mr Downes said the UV index will also be quite high this week as there will be less cloud cover and more sunshine.
“On Thursday, there will be more widespread temperatures above 26C over much of Leinster and Munster and the coolest parts will be up around Donegal and the fringes of Mayo and Sligo but you’re still looking at 21C to 24C in those regions,” he said.
“The entire southern half of the country could see temperatures reach up to 28C or 29C on Friday.
“Saturday is a similar sort of day with maybe a degree higher, it could reach 29C in some parts. It will be cooler though over northern fringes with 21C to 24C forecast.
“The southeast of country will be the warmest on Sunday with temperatures possibly reaching 29C in Carlow and Kilkenny.”
Meanwhile Seán Moynihan, CEO of ALONE said they were "reminding older people to take care and exercise caution in the heat, as this is a group which are at risk in extreme weather conditions”.
He said: “Heat exhaustion and heat stroke can be very harmful to over 65’s, particularly those who live alone or have existing health conditions. It is important to stay cool, drink plenty of water and to wear sunscreen and a hat when spending extended periods of time outdoors. We are used to extreme weather in winter but extreme summer weather can cause serious problems also.”
He continued, “We are also calling on all members of the public to remember their older neighbours, friends and relatives living alone and to consider their needs; if there is anything you think you can help with, no matter how small, even dropping in cold bottled water. It could make a world of difference to an older person during these challenging times.”