Temperatures are set to pass the 30° mark on Wednesday and Thursday, according to Met Éireann.
A High Temperature warning for Ireland remains in place, with hot conditions by day and staying very warm and humid at night.
Daytime maximum temperatures will be 27 to 30°, with overnight values not falling below 17 to 20°.
A separate status orange warning has been issued for Cavan, Monaghan, south Leitrim, Roscommon, Longford and Westmeath from 2.00pm on Tuesday.
Met Éireann says this will see maximum temperatures exceeding 30° in places, and overnight temperatures dropping no lower than around 20°.
Both alerts are in place until Friday.
Head of forecasting with Met Éireann, Evelyn Cusack, told Newstalk Breakfast the situation could change slightly at the weekend.
"The heatwave continues over the next couple of days - temperatures reached 29° yesterday in Tipperary, it'll exceed 29 today.
"And during Wednesday and Thursday it's likely to hit 30, perhaps 31° over parts of the midlands and west.
"For Friday and the weekend, while still warm and humid, there's an increasing chance of thundery showers breaking out.
"Even today there's a slight risk of a thunderstorm over the north midlands and west.
"But for most areas dry, hot and sunny today".
And Evelyn says people should be trying to keep heat out of their homes.
"The advice is to stay in the shade in this strong sun and the very high temperatures - and pull your blinds and curtains in your house [on] any south-facing windows in particular.
"Keep the sun out of the house, because the night-time temperatures are staying very high.
"At midnight, the air temperature is still close to 23°, so the minimum temperatures we give aren't until dawn.
"So very warm, humid nights over the next couple of nights".