The Head of Forecasting with Met Éireann has said it is 40 years since Ireland has experienced a heatwave during June like has been just experienced.
Gerard Fleming warned that because of very warm nighttime temperatures, people with respiratory difficulties should not take unnecessary exercise of a "vigorous kind" but rather stay where it is cool and allow their bodies to cool down
Mr Fleming said we have had five days where the weather is well above normal.
He said a heatwave is defined as five consecutive days when the temperature is 5C above normal.
Normally at this time of the year temperatures peak at 16 to 18 degrees Celsius but the last five days has seen temperatures in the mid-20s, even though today - which was actually the warmest of those five days - was the last day of the heatwave.
Mr Fleming said temperatures in Phoenix Park in Dublin reached 28.6C, which is 2C warmer than the peak earlier this week so while today was not as sunny as other days this week, it was the warmest day.
He said it is quite unusual to see temperatures this high during June in Ireland.
Temperatures in Ireland normally reach a peak at the end of July and into early August and that we are still on a rising curve of summer temperatures.
He said that to get these temperatures at this time of year is a real bonus.
He also said the highest temperature through the night and day yesterday at Valentia in Co Kerry was actually at midnight last night.
He said that it is extremely difficult to sleep when you get those temperatures close to 20C combined with humidity.
Mr Fleming added that this was why Met Éireann issued a Status Yellow heat warning for today, to highlight the issue more of the nighttime temperature rather than the daytime temperatures.
He said it is the high nighttime temperatures that stress the body and lead to some health effects.
He said that even though 26C and 27C does not sound too much for Ireland, academic research conducted at Dublin Institute of Technology showed that once temperatures start climbing into the high 20s hospital admissions begin to go up.