The Met Office has said sunshine and soaring temperatures show no sign of abating.
In an update on Thursday morning they report there is a 90% probability of heatwave conditions between 9am on Thursday and 9pm on Friday in parts of England.
The country experienced the hottest day of the year so far on Wednesday, with the mercury hitting 32.2C (90F).
Temperatures are expected to hit 30C (86F) again on Thursday, according to MeteoGroup.
Forecasters have said Britain is in the midst of its first prolonged heatwave since 2006, with six consecutive days of temperatures above 30C (86F).
It is set to continue into next week with temperatures in the high 20s Celsius at the weekend before rising to 30C and above next week - bringing with it an increased risk of thunderstorms.
Gemma Plumb, a forecaster with MeteoGroup, said there was no sign of temperatures dropping significantly in the coming days.
‘On Saturday and Sunday it looks like we will have temperatures of around 28C (82.4F) but by Monday we have temperatures of 29C and 30C, with an increased risk of getting some showers,’ she said.
‘Today there is a risk of thunderstorms across parts of south-east Scotland, South Wales and south-west England, but the rest of the country should remain dry.’
MeteoGroup said average rainfall for England and Wales so far this month was only 15% of the average at 4.9mm.
The Met Office said the UK had seen 132 hours of sunshine between July 1 and July 15, which is 77 % of the average for the whole month.
Average daytime temperatures have been 2C above average, it said.
Public Health England (PHE) officials have advised people to stay cool, drink lots of cold fluids and keep an eye on those they know to be at risk.
Dr Angie Bone, heatwave plan leader for PHE, said: ‘In this continued hot weather, it’s important to remember that high temperatures can be dangerous, especially for people who may be vulnerable such as older people, young children and those with serious illnesses.
‘During very hot weather, pregnant women and people who have chronic illnesses, including cardiovascular, respiratory, renal conditions, diabetes or Parkinson’s disease, may experience discomfort if indoor temperatures are particularly hot and in using public transport.
‘Employers should ensure indoor areas are kept cool and consider allowing these individuals to travel to or from their place of work during cooler, or less busy, times of the day.
‘For those working or exercising outdoors, strenuous physical exertion during the hottest part of the day should be kept to a minimum.’
Reports of dogs being left in cars with windows closed in the sweltering conditions have prompted warnings from the police.