Parts of Britain could see temperatures rise to 35C (95F) towards the end of the week as the heatwave continues.
Sun worshippers basked in the hottest temperature of the year so far on Monday, with a scorching 33.3C (92F) recorded in England, and the warmth is set to stay for the rest of the working week.
Temperatures hovered around 21C (70F) in parts of East Anglia and London past midnight, around the average July day time temperature for the region of 19-23C (66-73F) before dropping to around 18C (64F).
Monday's 33.3C high was recorded at Santon Downham in Suffolk, but it is set to get even hotter, with temperatures expected to peak on Thursday and Friday.
Becky Mitchell, Met Office meteorologist, said temperatures of 35C were forecast for Thursday in East Anglia and London, adding: "There's potential it could go even warmer than that.
She said the climbing temperatures are due to warm air coming up from France combined with high pressure across the country.
A respite from the heat could come by the end of the week, when thunderstorms are expected in eastern areas.
An amber "heat health watch" warning has been issued for parts of England.
The amber, or level three, warning is issued when temperatures are predicted to hit 30C (86F) during the day, and 15C (59F) at night, for at least two consecutive days.
There is a 90% possibility of heatwave conditions between 9am on Monday and 9am Friday in parts of England, mainly in the south and east.
The hottest July day on record is 36.7C (98F), which was reached at Heathrow on July 1 2015.
The Met Office said several places have had 54 consecutive dry days, starting May 30, including a few which have had less than 1mm of rain in the entire 54-day period - the longest spell since 1969, when 70 days passed with no significant rainfall.