The Met Office is considering issuing a rare amber or red extreme heat warning ahead of temperatures of 36°C or higher this week.
Parts of the country are preparing for their fifth heatwave of the summer as the UK continues to suffer through an unprecedented period of hot, dry weather.
Temperatures are set to rise again tomorrow after slightly cooling off today.
‘We’ll probably see highs reaching the mid-30s quite widely on Wednesday, and indeed on Thursday too for England and Wales,’ Met Office meteorologist Tom Morgan said.
‘On Wednesday, probably the Midlands, maybe a little bit further south, the M4 corridor, west of London, up towards the Midlands, is where we might have a small chance of reaching 36C in one or two spots.
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‘But Thursday at this stage looks the most likely hottest day of the week.
‘So 36°C is a fairly reasonable probability locally on Thursday and there’s a small chance it could get even higher than that.’
Half of England and all of Wales are experiencing drought conditions and more regions could be placed under them when officials meet at the National Drought Group today.
Morgan added: ‘If it wasn’t for this incredible summer that we’re currently seeing, then we’d be talking about these temperatures as being really, very unusual.
‘But of course, we’ve had such an exceptional summer, people have become a bit used to it.
‘There is a potential for impacts, so impacts to infrastructure, things like railway lines and power networks, impacts to vulnerable people as well.’
Health officials have warned of significant impacts to health and social care and a potential rise in deaths because of the heat. Nearly 3,000 excess deaths were caused by extreme heat in May and June in England and Wales alone.
Yellow heat health alerts issued by the UK Health Security Agency are in place for the East Midlands, West Midlands, the southeast, the southwest, the east of England, Yorkshire and the Humber, and London.
The alerts continue until 9pm on Tuesday, but may be extended.
Meanwhile, the Met Office is considering issuing rare extreme heat warnings ahead of the scorching temperatures forecast later in the week.
‘We sometimes issue extreme heat warnings, amber and red warnings, which we did back in June, so that’s under consideration at the moment,’ Morgan said.
More than 25 million people have restrictions on water use, the Environment Agency said, with millions under hosepipe bans, including all South East Water and Thames Water customers.