The record dry spell has been credited with the discovery of a previously unknown monument beside Newgrange in Co Meath.
The image of what appears to be a henge or circular enclosure with an entrance was captured by a drone on Tuesday.
The age of the henge is not known but it is believed to date from 2,500BC, some 500 years after the Newgrange megalithic tomb was built.
The drone that captured the image belongs to local historian Anthony Murphy.
"The weather is absolutely critical to the discovery of this monument. I have flown a drown over the Boyne Valley regularly and have never seen this," he said.
He said the bit of moisture left in the soil "lodges in the archaeological features a little bit more than it does in the surrounding soil and the crop that is growing out of the soil is greener in the archaeological features and drier outside of them.
"So when that crop is harvested all surface traces of this monument will vanish and we may not see this monument again for two or three decades depending on when we get another prolonged dry spell like this."
Mr Murphy estimates the henge, which is on private land, is up to 200 metres in diameter. It is the third henge to be found near Newgrange. While the two other henges were known about, one of them can also be seen in detail at the moment because of the parched landscape.
The National Monuments Service at the Department of Culture, Heritage and the Gaeltacht, last night thanked Mr Murphy for reporting his discovery to it.
It will now carry out technical work to determine the nature of the site, "but from the drone images...it is a very significant find".
Meanwhile the dry weather is set to continue with Housing Minister Eoghan Murphy warning that there is a risk of water shortages in September unless there is significant rainfall soon.
Speaking on RTÉ's 'Drivetime', he said: "The level of rain is nowhere near what we need to replenish our lakes and reservoirs."
Temperatures are due to peak at 25C today with only isolated showers being forecast for Ulster.
Met Éireann meteorologist Joan Blackburn said: "Friday will see a lot of dry weather and Saturday and Sunday will see the odd shower but there will be no major rainfall."