Fire crews have been battling dozens of fires across the East on a day which has already been declared the UK's hottest on record.
By 3.15pm the temperature in Cambridge had reached 39.9C, while Santon Downham in Suffolk - which reached a UK-wide high of 38.1C on Monday - had hit 39C. Highs of more than 40C are expected in East Anglia later in the day.
At Clacton-on-Sea in Essex, a search operation was launched to find a missing man who had been swimming in the sea after five others were pulled from the water.
Fire services across the region have reported a surge in calls, with crews called to wildfires burning in fields dried up by the hot weather.
Norfolk Fire Service declared a major incident, calling in extra staff to help cope with the number of calls and incidents.It urged the public to only call in for emergencies to allow crews to prioritise the most serious shouts.
Earlier in the day, firefighters battled to save homes in the Norfolk village of Ashmanhaugh near Wroxham, where a field fire had apparently spread to two houses in School Road.
In video footage filmed by a neighbour, one of the properties appeared to have been gutted, with flames seen burning through windows and the roof.
While at Wild Ken Hill in Norfolk - site of the BBC's Springwatch programme - a fire raged through the coastal park which is home to thousands of species of animal.
Reserve manager Dominic Buscall tweeted that it was "too early to say how bad the damage is, but certainly much wildlife lost. Climate change is here and we need a massive acceleration in our efforts against it."
Overnight, on the Norfolk-Suffolk border, six fire engines were needed to tackle a blaze in Thetford forest.
Appliances from both counties were sent to the forest fire at Brandon Road, just a mile from Tuesday's hot spot Santon Downham.
Meanwhile, a section of the A14 in Cambridgeshire began to break up in the heat, while train services were drastically scaled back for safety reasons.
The East Coast Mainline, which runs through Peterborough and Stevenage to London, will be shut this afternoon.
The Midlands Mainline between Luton, Bedford and St Pancras is also closed.
Services on the Avanti West Coast line, which runs to the north from London Euston and serves stations including Milton Keynes and Northampton, have also been suspended due to a fire on the line at Harrow in north London.
Many schools across the region have also closed, with health authorities warning people to take extra precautions in the heat for the sake of their health.
Temperatures have reached 40C for the first time on record in the UK, with 40.2C provisionally recorded at London Heathrow, the Met Office said.
The threshold - which eclipsed the previous record of 38.7C in Cambridge in 2019 - was hit at 12.50pm as much of the UK sweltered in a heatwave, with parts of England and Wales under a red warning for extreme heat, posing a danger to life, pressure on the NHS and disruption across transport networks.
The extreme heat is fuelled by climate change, which is making every heatwave more intense, frequent and likely, scientists warn.
The new high for daytime temperatures comes after the UK experienced its warmest night on record on Monday, with temperatures remaining in the mid-20s.
The Met Office warned temperatures were still climbing early on Tuesday afternoon.
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