Temperatures could hit 29C (84F) in parts of Britain today as health officials issued a heat warning amid concerns over a heightened risk of death for the vulnerable.
The Met Office said the South East of England would see the best of the weather this afternoon, although the mercury would return to highs of 24C (75F) tomorrow.
And the UK Health Security Agency issued a yellow heat health alert for London, South East, East and East Midlands - running from 1am today until 9am tomorrow.
The warning said: 'Minor impacts are probable across the health and social care sector, including increased use of healthcare services by the vulnerable population.'
It added that there would be an 'increase in risk of mortality amongst vulnerable individuals and increased potential for indoor environments to become very warm'.
People walk across Millennium Bridge in London in the warm summer sunshine this afternoon
Low-lying tinted clouds are seen on an overcast morning at Dunsden in Oxfordshire today
Met Office meteorologist Alex Burkill said: 'There's a bit of a mix in our weather across the UK - yes, there's some hot sunny weather towards the South East.
'But elsewhere it's a bit cloudy and there will be some rain at times - partly due to the same front that brought the rain through yesterday for many places.
'That's clearing away and then we will have showers towards the North and West on Thursday before an area of high pressure becomes more dominant as we go towards the end of the week and into the weekend and this will settle our weather down.
'So, turning largely dry - not necessarily totally dry, but nonetheless it is going to be a relatively quiet period as we go into the weekend.'
The outlook is slightly cooler between tomorrow and Sunday with highs of between 23C (73F) and 26C (79F) in London each day, but conditions will remain settled and dry.
The UK Health Security Agency (UKHSA) has issued a yellow heat health alert for London, South East, East and East Midlands, running from 1am today until 9am tomorrow
Explaining more about today's conditions, Mr Burkill said a weather front would bring cloud and rain across the North and South West of England and Wales this morning, before pushing further northwards.
Wales and the South West should turn mostly dry by the afternoon while in the East and South East it will be a 'pretty dry day - not as much sunshine as there was yesterday perhaps, but nonetheless largely fine'.
Mr Burkill continued: 'Across Scotland and Northern Ireland though, some showery rain coming in from the West - and some of this could be quite heavy and could bring some more persistent spells for a time.
'In the North West temperatures aren't really too far away from average for the time of year - high teens, just about getting into the low 20Cs perhaps towards some eastern parts of Scotland.
Sunseekers on Hive beach at Burton Bradstock on the Jurassic coast in Dorset yesterday
'But ahead of the front towards the South and East, here we have some hot air and so temperatures are going to be a little bit higher than they were yesterday - highs of around 27C, 28C, perhaps even a bit higher than this. So, feeling hot for some in any sunshine towards the South East.'
This evening, the front should clear away towards the North East along with most of the showery rain, so it should be dry and clear for most areas overnight.
However, Mr Burkill continued: 'That being said, some further showers will then push into parts of Western Scotland - perhaps some for the far west of Northern Ireland, England and Wales as we go towards dawn on Thursday.
'But many places (are) holding on to the dry and clear weather and, with fresher air coming in behind that front, it is going to be a bit of a cooler night this coming night than it was last night.
'Not especially chilly - most towns and cities holding up in double figures - but away from the more built-up areas, it will just about drop into single figures for some of us.'
Lyme Regis in Dorset was packed with sunbathers enjoying the weather on Monday
Tomorrow will bring a fresher start than this morning, with showers in western Scotland which then become more widespread north of the border.
Mr Burkill said: 'Plenty of showers also for Northern Ireland and some developing across parts of northern England and a few for Wales but towards the South and the East of England it's actually looking largely dry.
'I'm not really expecting any showers to push through here - it should be a fine day. Yes, some decent sunshine, but again because of that fresher air that's coming in temperatures aren't going to be as high as today.
'So we're looking at highs of around 23C, 24C towards the South East - so feeling pleasantly warm in the sunshine. And further north and west, mid to high teens really at best.'
He added that there would be more showers towards the end of the day tomorrow - but high pressure would become more dominant through Friday and into the weekend, 'so things are really going to settle down - lots of dry weather to come'.
There are currently no signs in the forecast for temperatures to get near those recorded on the UK's hottest day of the year so far, which was August 12 when Cambridge hit 34.8C (94.6F).
