The Met Office has issued a red weather warning for extreme heat in parts of south-east England from 09:00 BST on Wednesday to 21:00 on Thursday.
It said: “An exceptional spell of hot and humid weather is expected, with impacts to the general population highly likely.”
Forecasters believe temperatures could reach 38C (100F) in the South East by Wednesday, with one Surrey hospital already declaring a critical incident.
South East Water is asking customers to conserve water, with problems to supply already reported in Maidstone, Kent, along with problems caused by a burst water main in Crawley, West Sussex.
Weather expert Jim Dale told BBC Radio Surrey this week’s temperatures could “obliterate” previous records.
“June’s record is 35.6,” he said. “Records normally fall by tenths of a degree, not two or three degrees, that’s just ludicrous.
“That happened also in May when we got 35.1, that beat the previous by a couple of degrees. Something’s going on beyond what you might call a normal heatwave.
“Climate change is involved, global warming’s involved, that exacerbates the situation.”
