Rare 'red' extreme heat warning may be triggered as temperatures head towards 40C

Forecasters are considering issuing a rare Red extreme heat warning for later this week as the mercury heads towards 40C. Temperatures could reach 36C or higher this week, forecaster have said, with possible impacts to railway lines and power networks.

Parts of the UK are set to see their fifth heatwave of the summer as the country continues to bake in an unprecedented period of dry, hot weather. Well 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.

But Thursday at this stage looks the most likely hottest day of the week. So 36C is a fairly reasonable probability locally on Thursday and theres a small chance it could get even higher than that.

Half of England and all of Wales have been plunged into drought and more regions could be declared when officials meet at the National Drought Group on Monday.

Mr Morgan said: If it wasnt for this incredible summer that were currently seeing, then wed be talking about these temperatures as being really, very unusual.

But of course, weve 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 the effect on vulnerable people in the upcoming hot weather, with significant impacts possible in health and social care settings and a potential rise in deaths because of the heat.

Yellow heat health alerts issued by the UK Health Security Agency are in place for the East Midlands, West Midlands, South East, South West, East of England, Yorkshire and the Humber, and London.

The alerts continue until 9pm on Tuesday (August 11), but may well be extended as the hot weather continues. 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 thats under consideration at the moment, Mr 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.

Another record is set to tumble this week after Sunday was the 34th day so far this year when temperatures exceeded 30C somewhere in the UK, equalling the record from 1995.

So far, the extreme weather of summer 2026 has included two record-breaking heatwaves in May and June that led to more than 2,800 excess deaths. Two more heatwaves in July, the driest July in England and Wales since records began in 1836, have fuelled drought and wildfires.

The European Unions earth observation programme Copernicus said average temperatures across western Europe reached 21.61C (70.92F) for June-July, breaking the record set in 2022. Globally, this year is just behind 2024 and 2025 as the third hottest year on record.

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