The Met Office says that warm and humid air will move in today (Monday August 21) from the south.
Inland, Sussex is likely to see temperatures as high as 27degC tomorrow and Wednesday.
However, cooler and fresher air will be pulled in from the west later on Wednesday. with the temperature dropping back to around 20degC in Sussex and a couple of degrees colder further north.
Currently, the outlook for the Bank Holiday weekend is for cloudy but dry conditions on Saturday and sunny spells on Sunday, remaining in the low 20s degC.