It comes after highs of 29.5C on Tuesday, recorded in Monks Wood, Cambridgeshire, and a peak of 26C at Fyvie Castle, in Aberdeenshire.
The Met Office temperature prediction for Belfast on Wednesday this week is 20C, Thursday 17C, Friday 18C, Saturday 19C, Sunday 20C and Monday 21C.
The Press Association reported that temperatures on Wednesday are expected to be in the high 20s again across the south-east of England, with other parts of England and Wales seeing low-to-mid 20s and high teens or low 20s in Scotland and Northern Ireland.
Thursday and Friday will bring temperatures in the low 20s to areas of England while northern parts of the UK are likely to see 18C to 20C.
But they will again climb to the mid-to-high 20s in the south-east of England on Saturday and Sunday and low 20s in northern areas.
Met Office meteorologist Craig Snell said: “As we go into Thursday and then towards the weekend, high pressure – which has made itself at home across the UK this summer – is re-establishing itself as we go through to the end of the week and into the weekend.
“A lot of the UK will probably see a dry weekend with the best of the sunshine in the South.
“After potentially a couple of fresher days, Thursday and Friday, temperatures kind of climb once again as we go into the weekend.”
Tuesday’s rainfall in the north Midlands and northern England is set to move to southern parts of the Midlands, into central and southern England and East Anglia on Wednesday, but is expected to become lighter.
The rain comes after the driest July in England since records began, according to provisional figures from the Met Office.
Mr Snell added: “No real major signs of anything wet coming through for the South and generally the kind of warm theme is continuing for a lot of the country after a very brief cooler spell on Thursday and Friday.”