The highest temperature of the year to date has been recorded with 27.5 degrees reached at Mount Dillon in Co Roscommon on Friday afternoon.
In Northern Ireland, the 27 degrees mark was also breached in Stormont, Belfast and Killowen in Co Down which recorded 27.6 degrees.
The previous high for the year was 25.6 degrees recorded at the Phoenix Park in Dublin on June 13th.
An earlier, preliminary reading for Mount Dillon recorded the temperature as 27.1 degrees, which was later updated.
It is expected to get even hotter on Saturday with the possibility of 28 degrees in midlands areas.
The hot spell will last at least up to and including next Wednesday and it will remain warm into the end of next week though there will also be showers.
The wave of warm weather is a result of high pressure that has been travelling northwards to Ireland, according to Met Éireann forecaster Andrew Doran Sherlock. The Azores High will bring with it warm spells of sunshine throughout Friday and Saturday, with slightly cloudier conditions predicted for Sunday.
He said the next few days will be “largely dry, very warm and pretty humid”. The humidity will last into the nights, with temperatures in the low to mid teens, which “could be slightly uncomfortable for some”, he warned.
Early predictions from the forecaster suggest showery conditions may beset the country from Thursday.
The temperatures over the next few days are “above average” for what would be expected in July, when 17 to 19 degrees is typical, Mr Doran Sherlock said.
The Department of Agriculture has issued a condition orange forest fire warning for the next week.
A high fire risk is deemed to exist in all areas where hazardous fuels such as dead grasses and shrub fuels such as heather and gorse exist. This risk phase is expected to peak on Friday, July 23rd.
Forest visitors should not use barbecues or open fires at any stage. Four units of Dublin Fire Brigade are currently battling a gorse fire on the Hill of Howth in Dublin.