Rare red warnings have been issued over extreme temperatures that are set to hit record highs for June this week, with impacts on health, schools, workers and transport.
The Met Office said the heatwave could see temperatures hit 38C to 40C in some parts of England and Wales, smashing the June record set in 1976 by several degrees Celcius as human-driven climate change intensifies the impact of a “heat-dome” settling over western Europe.
The hot conditions, which have been very rare in the UK until now, will be accompanied by high humidity, and very warm and humid nights which will make it hard for people to recover overnight, the forecasters added.
The UK Health Security Agency (UKHSA) issued the red health warning for six regions of England – the West Midlands, East Midlands, South East, South West, London, and east of England – from 1am on Wednesday until 11pm on Thursday.
This alert indicates “a risk to life for even the healthy population” as well as impacts beyond health and social care, with potential effects on transport systems, food, water, energy supplies and businesses.
It is the second red heat health warning to be issued, after the first in July 2022 when temperatures soared above 40C in the UK for the first time.
A separate amber health alert has also been put in place for the North West, North East, and Yorkshire and the Humber for the same period, the agency said, meaning the impact is expected to be felt across the whole of the health service in these areas.
Dr Agostinho Sousa, head of extreme events and health protection at UKHSA, said: “Very hot weather is forecast across large parts of England in the coming days and we are urging health and social care services across the country to ensure they are prepared.
“It is vitally important that people understand the risk posed by high temperatures like these, and take steps to keep themselves and their friends, families and neighbours safe.
“Simple actions like staying hydrated, avoiding the sun during the hottest part of the day, and keeping your home cool can make a big difference.
“It’s also important to look out for others, especially elderly relatives, neighbours, and those with underlying health conditions, to make sure they are aware of the forecast and following the necessary advice.”
It follows the Met Office issuing a red weather warning covering an area stretching from London to Swansea and Somerset to Birmingham from 9am on Wednesday and 9pm on Thursday.
It warns that “substantial changes” in working practices and daily routines will be required.
There is also a high risk of failure of heat-sensitive systems and equipment, with the loss of power and other essential services, such as water, electricity, gas or mobile phone services.
Significantly more people will likely visit coastal areas, lakes and rivers, leading to an increased risk of water safety incidents, the Met Office said.
An amber weather warning is also in place for a larger area of England and Wales between Monday and Thursday.
Dr Will Lang, chief meteorologist at the Met Office, said: “We are forecasting extreme temperatures in the next few days, particularly on Wednesday and Thursday, when it looks like we’ll be seeing maximum temperatures into the high 30s.
“But also we are stressing very high overnight temperatures which will be very uncomfortable for vulnerable groups, and very humid conditions as well.”
He told the Press Association the conditions would far exceed the heat seen in June in the past, and was on “a much bigger scale” than the heatwave the UK experienced recently at the end of May.
Dr Lang also said the extreme heat would be of greater longevity than the record heatwave in 2022, when, for a “short, sharp” period, temperatures climbed above 40C in some places for the first time ever in the UK.
Fire chiefs are urging the public to take extra care in outdoor spaces as this week’s “dangerous” heatwave increases the risk of wildfires and water-related deaths as people flock outdoors to enjoy the sunshine.
Phil Garrigan, National Fire Chiefs Council (NFCC) chairman, said: “We have already seen the consequences that periods of extreme heat can have, with a number of lives tragically lost in water-related incidents during recent hot weather.
The Met Office said people can also expect travel disruptions, including delays on roads and road closures as well as delays and cancellations to rail and air travel.
Rod Dennis, road safety spokesperson at RAC, warned that there could be a record number of breakdowns this week as the heat puts extra strain on vehicles.
He urged drivers to take the red extreme heat warnings seriously and avoid non-essential journeys if their vehicles do not have effective air conditioning.
“The heatwave will affect services right across the UK and while all patrols will be working incredibly hard to assist drivers, longer waits are more likely,” he said, adding that some simple basic checks under the bonnet could reduce the risk of breakdowns.
The AA said drivers could also see gritters out on some roads this week with the potential for surfaces to soften or become sticky under the heat, with heavy traffic even causing them to rut in some places.
Edmund King, AA president, said: “If drivers come across a softened or damaged surface, they should slow down, avoid harsh braking or steering, and leave extra space from the vehicle in front.”
Meanwhile, the National Association of Head Teachers (NAHT) said it has written to all its members with guidance on dealing with the heat this week, including impact on pupils and staff, legal positions and when to consider closure.
Paul Whiteman, NAHT general secretary, said: “While there is no legal ‘upper limit’ for temperature in schools, (school leaders) will certainly be doing all they can to mitigate the effects of such high temperatures.”
And employers are being urged to assess any risks to workers as the heatwave kicks in, with conciliation service Acas saying they should assess any risks and discuss what they need to do, such as providing fans, portable air-cooling units, allowing more frequent or longer breaks and relaxing rules for wearing ties or suits.
Ruth Wilkinson, of the Institution of Occupational Safety and Health, also warned that outdoor workers, such as those in agriculture, construction, and the gig economy, face the most immediate risks.
“But indoor workers aren’t immune as poor ventilation, lack of cooling infrastructure, and outdated building designs mean many are left to work in stifling conditions,” she said.
Scientists said the cause of the heatwave is similar to the “heat dome” seen last month, which involves a “high-pressure” weather system stalling over a region and trapping heat.
Akshay Deoras, senior research scientist at the National Centre for Atmospheric Science at the 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 that human-driven climate change “has provided the springboard for this event” after loading the atmosphere with extra heat and making extreme temperatures far more intense than they would have been in the past.
Bill McGuire, professor emeritus of geophysical and climate hazards at University College London, said temperatures of more than 43C are now possible in the UK’s current climate, with heatwaves lasting for multiple days.
But the country’s health services, energy infrastructure and transport are “simply not built for these conditions,” he warned.
And Gareth Redmond-King, head of international at the Energy and Climate Intelligence Unit, said the heatwave “hits in the week Parliament is set to debate and vote on the UK’s plans to get to net zero – which remains the only scientifically available solution to halting climate change, and limiting these dangerous and costly extremes into the future.
“Let’s be clear, temperatures will continue to go up and up until we reach net zero emissions.”
Last week, the national drought group, which brings together the Met Office, regulators, government, water companies, farmers, scientists and conservation organisations, said the risk of drought has risen as East Anglia returns to the status of “prolonged dry weather” and while Devon and Cornwall are on a watchlist.
Farmers are also facing growing pressure, the group said, with many reporting issues with the growth of spring crops which forced them to start taking water from rivers and lakes to sustain crops in dry soil earlier than usual this year.
Officials said the Environment Agency is working with water companies on their drought plans and is actively monitoring water levels and rainfall patterns.
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