Met Éireann has issued a Status Orange thunderstorm and rain warning for Galway, Clare and north Tipperary.
A line of intense thunderstorms will move through parts of counties Galway, Clare and north Tipperary this afternoon.
Early evening will bring lightning, hail and torrential downpours giving localised flooding in places, with very hazardous driving conditions.
Earlier Met Éireann issued a Status Yellow thunderstorm and rain warning for the whole of Ireland, as the hot weather is set to remain into the weekend.
The warning, which lasts until 8pm, advises that thunderstorms will affect a number of areas this afternoon and evening.
Lightning, hail and heavy downpours will result in localised flooding and hazardous driving conditions, Met Éireann said.
The counties most at risk from the Status Yellow warning are Wicklow, Kildare, Laois, Offaly, Tipperary, Clare, Galway, Mayo and Roscommon.
Alongside the thunderstorm risk, heatwave conditions are persisting with Met Éireann forecasting that temperatures will reach into the high 20s and possibly above 30C today.
A Status Yellow hot temperature warning is in place for the country until at least 9am tomorrow.
Met Éireann communications meteorologist Bonnie Diamond said that the warm weather conditions will continue over the weekend, with temperatures expected to be in the low to mid 20s and some good sunny spells.
The seven-day duration of the current heatwave is "quite exceptional", she said, where temperatures have been in the high 20s and 30s day after day.
A tropical night temperature of 20.5C overnight was recorded in Valentia in Co Kerry, and the top temperature recorded was 31C at Mount Dillon in Roscommon.
Intense thunderstorm activity continues across north Munster & into south Connacht as seen in the video below.— Met Éireann (@MetEireann) July 23, 2021
Take care if driving in the affected areas as lightning, hail & torrential downpours will lead to very hazardous driving conditions.??????
Speaking on RTÉ's Morning Ireland, Ms Diamond said that record-breaking temperatures have been recorded in Northern Ireland over the last week, where records were broken three times day-on-day and reached 31.4C in Armagh yesterday.
She said the very warm and humid overnight temperatures are very rare, and have been seen only on a handful of occasions since digital records began in the 1940s.
Met Éireann plans to study the climate signals behind the heatwave.
Ms Diamond said there has been extremely unusual weather patterns observed in parts of the world recently, some of which had previously been deemed "virtually impossible".