Highs of over 28 degrees were recorded in Waterford yesterday.
Met Éireann's high-temperature advisory will run until Friday with very warm conditions forecast.
Yesterday's temperature of 28.2 degrees recorded in Waterford City made it the hottest day recorded since 2018.
Michael Kelly from Waterford Weather recorded 29.2 degrees in 2018, but he says the current humidity rates make conditions feel even warmer.
"Back in 2018, the humidity levels were a lot lower but right now the levels are around 60 to nearly 70% and people are sweating a lot more.
"People are saying it's very muggy and it is because the humidity levels are higher and the heat is high as well so it feels a lot hotter than it did in 2018 when we broke those records," Kelly said.
The conditions are set to continue until the end of this week and Michael says yesterday's high of 28.2 in Waterford could even be broken on either Monday or Tuesday.
"High pressure looks to dominate for most of this week at least up until Thursday we'll be keeping these high temperatures mid to high 20s.
"There may be a little breakdown on Friday with a low pressure pushing up from the South but that's still not certain.
"Even when that breakdown does come it's still going to be relatively warm around 23-24 degrees celsius so we're going to be holding onto the heat into next weekend although it might be a bit more unsettled, " Michael Kelly said.
