The Anglia region could see the hottest September day in more than 50 years as temperatures soar.
Temperatures on Tuesday are expected to peak between 30°C and 32°C in the South East. It means Britain could be as warm as Bangkok in Thailand, and hotter than predictions for Madrid and Los Angeles.
The last time temperatures soared above 30°C in September was in 2006 in Kew Gardens, which hit 30.5°C on September 11.
If the mercury rises above 31.6°C, which was reached at Gatwick on September 2 1961, then it will be the hottest day for 55 years.
Britons can expect to bake in above-average temperatures across the UK for the rest of the week, the Met Office said.
Conditions will become more unsettled on Thursday and Friday when a band of rain will sweep east, bringing scattered showers.
Already by lunchtime on Monday temperatures in the Anglia region had reached 25°C at Shoeburyness in Essex, which is 6°C above average for the time of year.
The highest September temperature recorded was in 1906 when the mercury hit 35.6°C in Bawtry, South Yorkshire.
The highest September temperature ever recorded in the Anglia region was 34.6°C at Raunds in Northamptonshire on 8 September 1911.
Maximum temperatures in the Anglia region on Monday 12 September 2016
- 27.0°C in Writtle, Essex
- 26.6°C in Shoeburyness, Essex
- 26.6°C in Cavendish, Suffolk
- 26.5°C at Norwich airport
- 26.2°C in Santon Downham, Suffolk
- 26.1°C in Tibenham, Norfolk
- 26.0°C in Cromer, Norfolk
- 25.9°C in Andrewsfield, Essex
- 25.4°C in Cambridge
- 24.1°C in Bedford
- 23.6°C in Wittering, Cambridgeshire
- 23.1°C in Northampton