Met Éireann has issued a weather warning for the whole country, saying possible heavy showers could lead to local flooding.
The forecast is for warm and humid weather tonight, tomorrow and on Saturday, with possible heavy showers and thunderstorms.
There is also a risk of hail.
The warning is valid from 9pm tonight until 9pm on Saturday.
Meanwhile, meteorologists in the UK have said that the weekend will see blistering heat, thunderstorms and the prospect of localised flooding.
Today is expected to be the hottest of the year, breaking the 30C barrier for the first time, with temperatures as high as 32C expected tomorrow as a belt of Iberian weather hits UK shores.
However, the thunder and heavy showers are also possible.
The Met Office to issue a severe weather warning for much of the country on Saturday, with the potential for localised flooding.
The hot, humid conditions prompted Public Health England (PHE) to warn of potential dangers, stating that heatwave conditions could have a "significant effect on health".
PHE said people should consider staying out of the sun during the hottest part of the day, drink plenty of fluids and wear sun cream that is at least factor 15.
It has also asked people to be aware of children and the elderly, to ensure they are not suffering because of the heat.
People should never be left in closed, parked cars, especially infants, young children or animals, a spokesman added.