Northern Ireland is due to experience a short warm spell today and tomorrow.
The hottest temperature is predicted to be 22 Celsius today and 23C tomorrow.
“Both days are looking pleasantly warm with some decent sunshine,” a spokeswoman for PA Meteogroup told the News Letter.
It will be more unsettled from Wednesday, with Thursday likely to be rainy most of the day.
England has already being experiencing fine weather. The hottest temperature in Great Britain today (Sunday) was 23.8 C at Gosport, Hampshire in the south of England, significantly ahead of the hottest in Northern Ireland today, at Helen’s Bay in Co Down, which reached 19.4C.
Billions of litres of extra water is being readied to pump into the south of England, with temperatures to straddle 30C (86F) this week.
Some 450 million litres of water per day is on standby – enough to fill 900,000 paddling pools, according to Thames Water
On a hot day, water consumption in London increases around 14% and this shoots up to 27% in Thames Valley as people escape the capital, the company said.
Alex Burkill, a meteorologist with the Met Office, said Britain would peak on Tuesday and Wednesday with temperatures breaking 30C.