The Met Office said some areas were edging close to recording an official heatwave this week as pupils head back to school.
Portsmouth, Gosport and Fareham have been predicted a potential high of 26C today while Waterlooville could see 27C, according to the Met Office.
On Monday, the maximum UK temperature was logged at 28.9C in Larkhill, Wiltshire, closely followed by the 28.8C recorded at Santon Downham, Suffolk, and 28.7C at Middle Wallop in Hampshire.
Greg Dewhurst, a Met Office meteorologist, said central and eastern England were the likely areas that could experience a maximum of 30C on Tuesday.
Mr Dewhurst said low pressure moving in from the south west on Wednesday make it ‘less hot’ in parts of Wales and Northern Ireland, but ‘hot air’ will remain in central and eastern England and Scotland, bringing highs of 26C to 29C.
Temperatures will fall later in the week, with an increased risk of some heavy showers.
Mr Dewhurst said central and eastern parts of England were ‘most likely’ to record an official heatwave across Monday to Wednesday, but will only ‘just about make it’.
A location meets the UK heatwave threshold when it records a period of at least three consecutive days of daily maximum temperature levels meeting or exceeding thresholds which vary across the country.
These include 25C for Wales, Scotland and south-west England, 27C for southern and eastern England and 28C for London.
“We often get a warmer spell particularly early on in September,’ Mr Dewhurst said, adding: ‘August was particularly cool… and cloudy, so this spell is the warmest spell of weather since July for the UK.’
September has already beaten this August’s highest temperature of 27.2C in the UK.
The current warm weather follows the official end of summer, from a meteorological point of view, which is considered to be August 31.