Heathland fires are still raging across parts of Ireland after the record-breaking dry spell.
Emergency services continued to tackle the fires as forecasters said there was very little chance of rain in the next 24 hours.
In Northern Ireland, police were investigating reports of a man seen with a petrol can close to one of the worst gorse fires for years in the Mourne Mountains.
Another two youths were spotted lighting fires in south Armagh, reports to the Police Service of Northern Ireland added.
Hundreds of acres of land are being destroyed, and homes and livestock threatened by fires which have burned for much of the bank holiday weekend in Counties Down, Armagh and Tyrone.
In Ireland, three Air Corps helicopters and more than 100 troops wearing specialist suits have been tackling wildfires in the north- west of the country.
The Defence Forces said operations were focusing on the Dungloe area of Co Donegal, where significant progress has been made.
Paul Knightley, a forecaster from MeteoGroup, the weather division of the Press Association, said it was unlikely to rain until tomorrow evening at the earliest.
He said: "We're not expecting any rain in the next 24 hours. There's an area of high pressure over the north of the country. Tomorrow night it looks like some showery rain will start to edge into Northern Ireland and it might start to edge into Scotland on Thursday morning."
The forecaster said Northern Ireland had just two-thirds of the rain it would normally expect in April with the 1.5in (38mm) that fell 66% of normal levels.