London heatwave ‘furnace’: Red extreme heat warning as capital to bake in record 40C temperatures

Scientists sounded the alarm over London being hit with temperatures “dangerously close to levels previously thought almost unimaginable in the UK”.

The heat could spiral to 40C in the capital in coming days in what could be the city’s hottest recorded week in June.

he Met Office has issued a rare red extreme heat warning for Wednesday and Thursday and Londoners should brace themselves for four “tropical nights” as temperatures stay above 20C, even once the sun has gone down.

The heatwave is forecast to last the full duration of the working week with little respite as the heatwave takes a hold on the capital. The high humidity in London is also expected to make the next few days especially uncomfortable.

Several schools have now announced plans to close over the course of the heatwave, citing “uncomfortable and potentially unsafe” environments for teachers and pupils. But commuters will have no such luck as it will be business as usual for the majority of the capital.

Eurostar has also cancelled a number of journeys to and from London due to the scorching temperatures while Paris battles temperatures upwards of 40C.

Last month saw the UK’s hottest-ever May day when a temperature of 35.1C was recorded in Kew Gardens.

The coming days are set to be even hotter, soaring past the previous record for June of 35.6C.

Dr Akshay Deoras, senior research scientist at the National Centre for Atmospheric Science & Department of Meteorology, University of Reading, said: “This is not just a heatwave, it is a heat-dome driven furnace that will grip most of southern UK and push temperatures into truly exceptional territory.

He added: “We are looking at an intense and record-breaking spell of heat with widespread impacts on public health, infrastructure and essential services. Unlike the heatwaves of May 2026 and July 2022, elevated humidity levels are expected to make conditions feel even more oppressive and dangerous by severely reducing the body’s ability to cool itself through sweating.

“Long-standing June temperature records are set to be shattered by 25 June, potentially by a significant margin, and with temperatures edging dangerously close to levels previously thought almost unimaginable in the UK.”

A heatwave in London is defined as when the temperature reaches 28C or above for three consecutive days.

Monday is set for a high of 29C before the mercury soars to a record-breaking 36C on Tuesday.

Temperatures could then reach as high as 40C on Wednesday and 39C on Thursday.

The heat is then expected to drop on Friday to a still-scorching 29C and 27C on Saturday.

If the temperature on Wednesday is as high as forecast, it could approach or surpass the record for London’s hottest-ever day. The hottest recorded day to date was a high of 40.2C in July 2022.

Weather expert Colin McCarthy stressed: “One of the worst heatwaves in European history is underway.”

An amber alert for extreme heat on Monday and Tuesday was extended by the Met Office until at least the end of Thursday following the forecast.

Greg Wolverson, deputy chief forecaster at the Met Office, said: “While heatwave criteria will be met for some in the south and south-east of England over the weekend, with temperatures into the low 30s possible, the warmth will expand and intensify at the start of next week, which, coupled with high temperatures overnight, leads to potential impacts.

“Temperatures will peak around the mid-30s on Monday and Tuesday. The humidity will also mean this feels close, warmer and more uncomfortable for many.

“Tropical nights – where the temperature doesn’t drop below 20C – are also likely for some.”