The Department of Agriculture has issued a Red Warning for forest fires which took effect at 9am yesterday morning and is effective until 12pm on Friday.
The high temperatures and drought conditions mean that there is an ''extreme fire risk'' in some areas.
It comes as footage emerged of the devastation of the forest fires in the Sally Gap area of Co. Wicklow last night.
Meanwhile, people are being reminded to be vigilant in the sun as the heatwave continues.
Many parts of the country are due to see long spells of sunshine again today with temperatures into the high 20s.
Dr Jim Gray, emergency medicine consultant at Tallaght Hospital in Dublin, said: "Plenty of drinks and cover up and not to be out in the sun for long periods and being sensible.
"We need to enjoy the sun, it's wonderful to have it, but to be safe and sensible is the main message."
