Britain will go into heatwave meltdown this week with schools closing early, roads melting and trains cancelled as the country braces for its hottest day in history.

The Met Office has today issued a rare red 'danger to life' extreme heat warning for 'significant disruption to daily life' as the UK faces major delays to road, rail and air travel.

As temperatures climb over the next few days to a near record-breaking 40C and indoor spaces become unbearable, schools could shut amid fears over the impact of overheating classrooms on children's health.

Some headteachers have already confirmed the school day will finish at lunchtime, while others are letting pupils come in wearing PE kits and cancelling sports days.

Meanwhile the RAC urged drivers without air-conditioned vehicles to postpone non-essential car journeys, while the AA said motorists could see gritters out in case surfaces soften or become sticky under the heat and even rut in some places under heavy traffic.

And on the trains, operators are planning to alter some services and introduce temporary speed restrictions as the heat causes overhead lines to expand and sag and rails to buckle.  

Rail passengers were furious at the schedule changes, with one saying on X: 'More notice would have been appreciated, given it's been known for over a week that temperatures would be over 30C.'

Another wrote: 'It is inevitable that the rail network will be subject to delays and cancellations, the railway simply isn't built for this sort of heat.' And a third tweeted: 'Britain and the weather. Heat expands and contorts rail tracks. Total disruption. Two inches of snow falls. Total disruption.'

Great Western Railway will be running a revised service between London Paddington and Didcot Parkway after Network Rail said it would not move some points to avert the risk of them failing – meaning Slough, Maidenhead and Twyford will not be served.

LNER, which runs between London and Edinburgh, is 'introducing temporary travel easements to support customers in completing their journeys more comfortably'.

The Met Office said 'population-wide adverse health effects are likely' while 'failure of heat-sensitive systems and equipment is likely with the probable loss of power and other essential services, such as water, electricity, gas or mobile phone services'.

The extreme heat will be accompanied by high humidity, and very warm and humid nights which will make it hard for people to recover overnight. The Met Office also urged people to adapt their routines where possible to cope with the weather.

The red warning is only the second ever, and will cover parts of central and southern England as well as Wales from 9am on Wednesday to 9pm on Thursday. A separate wider amber heat warning began today and will run until at least the end of Thursday.

One climate scientist said the 'heat dome driven furnace' will bring 'truly exceptional' temperatures, while a Met Office meteorologist called it a 'very serious situation'.

The UK Health Security Agency (UKHSA) meanwhile has upgraded its heat health alerts from amber to red for Wednesday and Thursday for much of England. Other amber heat health alerts will continue to be active from now until the end of Friday.

Red alerts warn of 'increased risk to life across the whole population, with significant impacts on older people'; 'significantly increased demand on all health and social care services' and the 'heat affecting the ability of the workforce to deliver services'.

There are also concerns about the impact on animals, and the British Horseracing Authority has already abandoned four meetings. 

Temperatures in southern England could hit 34C today then 37C tomorrow before peaking at 40C on both Wednesday and Thursday, followed by 33C on Friday.

The UK's all-time high of 40.3C was set in July 2022, followed by 38.7C in 2019 in second; 38.5C in 2003 in third; 38.2C in 2022 in fourth; and 37.8C in 2020 in fifth.

The highest ever June temperature is 35.6C both in London in 1957 and Southampton in 1976 – but this could be broken three times this week, and as early as tomorrow.

Humid conditions are also forecast for the country alongside tropical nights, when the overnight temperature does not fall below 20C, making it feel muggier than last month's heatwave – which itself brought the hottest ever day in May at 35.1C.

A record-breaking June day would be the first time since 1911 that two consecutive months have observed record temperatures. 

Brits are also struggling to get hold on portable air conditioning units amid a rush in demand. One X user tweeted: 'If you're in the UK all of the portable AC units are sold out from all of the stores. I've checked about buying an additional unit since last Thursday.'

Despite the increasing number of heatwaves in recent years, the Department for Education has no official upper limit on the indoor temperature for schools.

But the UK Government has been considering recommendations from the Climate Change Committee that indoor classrooms should be no higher than 25C.

The National Education Union says 26C should be a maximum and its heatwave plan for teachers states schools could close under a red warning for extreme heat.

Some schools are allowing students to come in wearing PE kits while others have confirmed they will operate with shorter days to protect the health of staff and pupils.

New Close School in Warminster, Wiltshire, said its site would close early at 12.30pm each day between today and Thursday 'due to the forecast of extreme heat'.

A statement said: 'This decision has not been made lightly and is in advance of the expected peak temperatures, with the safety and wellbeing of both children and staff as our highest priority.

'Current guidance advises that indoor rooms should be maintained at temperatures below 26C. Unfortunately, due to the age and design of the building at New Close, we are unable to maintain temperatures below this level during the forecast heatwave.

'Even with blinds closed and fans in use, rooms are heavily exposed to direct sunlight and retain heat throughout the day, making it difficult to keep temperatures within safe limits. The rooms are already hot and have retained the heat from Friday and over the weekend.'

Other schools in Wiltshire including Kingdown School, Clarendon Academy, Pewsey Vale School and Dilton Marsh Primary have also said lessons will finish at 12.30pm.

Katherine Warington School in Harpenden, Hertfordshire, said its sports day had been postponed until mid-July due to the heat; while St Anthony's Catholic Primary School in Slough, Berkshire, said sports day had been postponed by one week.

Meanwhile Oxted School in Surrey said students will be 'permitted to wear their PE uniform to school up to and including Thursday' because of the hot weather.

One secondary science teacher prompted a 33-page debate on Mumsnet yesterday by asking whether schools should be closed when temperatures reach 35C.

She said temperatures in her class hit 30C last week, adding: 'I had children saying they were dizzy and feeling sick, and they're made to go outside during breaks.

'I'm also not sure that anything I taught them during the extra hot days actually stuck in anyway as they all seemed melted onto the desks.'

One teacher said that it was 'definitely survival mode this week', while another claimed their school was 'literally like a giant greenhouse – lots of glass everywhere'.

But others were less sympathetic, writing that 'children go to schools in hot climates without air conditioning all over the world' and just need 'shade, be that outside or inside'.

Another said: 'We had hot weather in the 70s & 80s when I was at school, nobody had a water bottle - we just got on with it, everyone survived and nobody fainted.'

The NEU and NASUWT teachers' union have a joint action plan which states that schools could close if the Met Office amber warning is upgraded to red.

It says: 'Where a red alert is issued for extreme heat, school and college employers must ensure that an immediate, additional risk assessment is carried out and the control measures indicated are enacted.

'These could include full or partial closure of the site if the risk assessment deems this necessary.'

For an amber alert, it states: 'Travel delays are possible and there's an increased risk that heat-sensitive systems may fail. So, some changes to routines may be appropriate, following a risk assessment.'

Schools are encouraged to have a heatwave plan and 'curtail, so far as possible, heat-generating activities, for example, use of computer monitors, printers, Bunsen burners, ovens, and design and technology equipment, unless effective heat extraction measures can be put in place'.

Teachers can also 'relocate classes to cooler rooms whenever possible' and relax dress codes, such as allowing pupils to wear PE kits.

Catering staff 'should not be expected to prepare hot meals' while classrooms should have oscillating mechanical fans if temperatures are below 35C.

They should also 'remove vigorous physical activity from the timetable', while 'children may be better off indoors at break times if there is insufficient shade' and should 'avoid outside activities, such as PE and school trips'.

Paul Whiteman, general secretary for school leaders' union NAHT, said: 'As temperatures rise, school leaders will be thinking carefully about how to keep pupils and staff safe and as comfortable as possible.

'While there is no legal 'upper limit' for temperature in schools, they will certainly be doing all they can to mitigate the effects of such high temperatures.

'For most, this will mean making straightforward adjustments such as limiting the time spent in the sun during breaks, ensuring additional water is available, making adjustments to uniform expectations where appropriate, and ventilating classrooms as best they can.'

The AA said drivers could 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: 'The main risk for drivers is not that the road suddenly 'melts' everywhere, but that patches can become tacky or uneven. That can affect braking, steering and grip, especially for motorcyclists and cyclists, and can also throw up loose material.

'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.'

The AA also warned that heat can put extra strain on vehicles, with under-inflated, damaged or old tires particularly likely to fail in hotter conditions.

'Before a long journey, check tyre pressures, tread and sidewalls, and carry water in case you are delayed,' Mr King said.

'In these temperatures the advice remains never to leave passengers or animals unattended in parked cars even for short periods when the interior of the car can soon get as hot as an oven.'

RAC road safety spokesperson Rod Dennis said: 'Red extreme heat warnings are rare and we urge everyone to take them seriously this week.

'Drivers whose vehicles don't have effective air conditioning should strongly consider postponing any non-essential car journeys until the Met Office's weather warnings are lifted and temperatures drop.

'If this isn't possible, our best advice is to travel during cooler times of day. This is especially important for anyone travelling with vulnerable people, including young children and older adults, who are at greater risk from the intense heat.'

Met Office deputy chief forecaster Mark Sidaway said: 'Red warnings are reserved for the most severe events and we're expecting severe and significant impacts from this heatwave, with health impacts likely for many, even beyond those who are normally more vulnerable to the heat. 

'The last time the UK recorded temperatures this high was in July 2022, but on this occasion the heat is expected to be accompanied by high humidity.'

A static area of high pressure over mainland Europe is trapping warm air underneath - known as a 'heat dome' - and resulting in the very hot conditions for England. 

Met Office meteorologist Simon Partridge said that for today, central southern England could see highs of up to 34C with the temperature set to climb to 37C tomorrow in southern England and south-east Wales.

'Then Wednesday and Thursday, both 38C but there's potential for it to go higher and then by Friday, coming down a little bit, so we'll see 33C and then it should ease off into the weekend but still stay quite warm, even into next week, although it won't be anywhere near as warm as this week,' he added.

The Met Office said the red warning area 'now looks increasingly likely to see a two to three day period where maximum temperatures in the shade exceed 37C, perhaps rising to 38C to 40C in some places'. 

The Met Office had already issued an amber weather warning covering large areas of England and Wales from today until Thursday. 

This morning, officials upgraded areas of central England and Wales to red for Wednesday and Thursday.

The red alert stretches from London across to Somerset and Swansea and up towards Birmingham.

Met Office senior operational meteorologist Marco Petagna tweeted: 'A very serious situation unfolding. Red weather warning issued.

'40C now possible this week... this would be 4.4C above the current UK June temperature record... a truly astounding event. The all-time UK record set just four years ago in July is currently 40.3C.'

Responding to an X user who claimed he was 'scaremongering', Mr Petanga added: 'The purpose of the Met Office is to help people make better decisions to stay safe and thrive... issuing weather warnings is proven to assist in this process.' 

As part of the red warning, forecasters say conditions will bring a risk to life and population-wide health impacts that no longer limited to those most vulnerable to extreme heat while 'substantial changes' in working practices and daily routines will be required.

Significantly more people will likely visit coastal areas, lakes and rivers, leading to an increased risk of water safety incidents, the Met Office said.

And people can expect travel disruptions, including delays on roads and road closures as well as delays and cancellations to rail and air travel which bring significant welfare issues for those who experience even moderate delays.

Brits are advised to drink plenty of fluids and keep out of the sun, and avoid exercising between 11am and 3pm, the weather service said.

National Rail advised travellers to check their journeys in advance, allow for extra time and to carry water.

Mr Partridge said: 'It's a very unusual, very rare spell of very hot weather, so it's one of those ones where people should take care, try to keep their houses as cool as possible, check in on those that are vulnerable, so the very young and very old, in particular, are more vulnerable to extreme heat.

'But everybody will feel this because it will be very hot and the overnight temperatures, in particular, will mean that people won't be getting as much sleep, probably, as they would usually do, so it will affect everyone.

'There's also potential for impacts to transport as well.

'We know that when things get very warm, there can sometimes be issues with railway lines, and even possibility that some roads might not be doing too well.

'If it gets too warm, you may even see a little bit of Tarmac melting at times.'

The hottest temperatures are expected in areas between Bristol and London and south of the M4, with most of England and Wales set to hit more than 30C this week, he said.

Sir Sadiq Khan issued a 'high air pollution alert' for London today, saying: 'Hot, sunny weather and pollution from continental Europe are expected to raise ozone levels'

The London Mayor added: 'Please help protect yourself and others, especially vulnerable people, by reducing car journeys and avoiding engine idling.'

A rare UKHSA red heat health alert has been issued for six regions in England for Wednesday and Thursday.

The West Midlands, East Midlands, South East, South West, London, and East of England will be under a red heat health alert from 1am on Wednesday until 11pm on Thursday this week.

It is the second red heat health alert to be issued, after the first in July 2022 when temperatures soared above 40C.

An amber alert has also been issued for the North West, North East, and Yorkshire and the Humber for the same period.

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.

'A red heat health alert indicates a risk to life for even the healthy population, but 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.'

Angelo Makri, senior knowledge officer for wellbeing at Alzheimer's Society, said: 'It's important to remember that extremely high temperatures can pose serious risks for people living with dementia if they are not supported to stay cool, hydrated and out of the sun.

'People with dementia may not always recognise when they need a drink or wear suitable clothing, which can increase the risk of dehydration and heat-related illness. 

'With temperatures set to reach extreme highs this week, we're urging families, friends and carers to make sure loved ones are drinking enough, wearing light clothing and staying indoors as much as possible.'

The Met Office says a heatwave is defined as three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.

The threshold varies across the UK - between 25C across Scotland, Northern Ireland, Wales and South West England, and 28C in London and its surrounding counties.

Parts of the UK are now technically in a heatwave, after one was declared yesterday in Writtle, Essex, following three days in a row of 27C-plus temperatures – which is the local threshold.

The heatwave comes after at least 17 people died after getting into trouble in open water during the hot weather last month which was also unprecedented for the time of year.

Mr Partridge said: 'We're also asking as well for everybody to just be very wary around bodies of water, because in the last heatwave, unfortunately, quite a few people lost their lives by going into cold water and getting cold water shock.

'That's still very much an issue, so just be careful how you cool yourself down.

'If there's the option between a hose pipe and jumping in the lake, probably go for the hose pipe and just keep yourself safer.'

Simon Francis, co-ordinator of the End Fuel Poverty Coalition, said: 'Heatwaves of this magnitude pose a serious health threat. Millions of people are at risk of being made unwell by overheating in their homes, most of them in poorly ventilated properties with no affordable way to keep cool.

'With energy bills about to rise by 13.5 per cent, switching on a fan or running air conditioning is simply not an option for some people already in debt to their supplier. 

'What's worse, the Climate Change Committee has warned that 92 per cent of homes could overheat in more extreme heat events, and that the poorest neighbourhoods are seven times more likely to be vulnerable.

'It is a disgrace that not only are the fossil fuel giants contributing to the climate crisis, but they are also profiting from the increased energy prices households have to pay to keep our homes cool in the summer.'

The immediate cause of this week's heatwave is similar to the 'heat dome' seen last month, which involves a 'high-pressure' weather system stalling over a region and trapping heat, a climate expert said.

Liz Bentley, chief executive at the Royal Meteorological Society, said: 'The coming week will bring an unprecedented heatwave with temperatures likely to reach 38-39C.

'This will lead to two consecutive months, May and June, in which the UK temperature records have been annihilated by well over 2C.

She added that one of the overriding reasons we are experiencing more frequent and intense heatwaves 'is because our climate has changed due to the fossil fuel emissions leading to more dangerous extremes of heat'.

Dr Akshay Deoras, senior research scientist at the National Centre for Atmospheric Science, 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.

'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 June 25, potentially by a significant margin, and with temperatures edging dangerously close to levels previously thought almost unimaginable in the UK.'

The current heat comes after a mean temperature of 16.1C was measured between the start of June and the end of August in 2025, making last year the hottest UK summer since records began, according to the weather service.

The previous record was held by summer 2018, followed by 2006, 2003, 2022 and 1976.

Last summer saw four heatwaves and a hottest temperature of 35.8C recorded in Faversham in Kent, below the UK's all-time high of 40.3C which was measured in July 2022.

Last year saw consistently above-average temperatures throughout June and July and knocked the memorable summer of 1976 out of the hottest five UK summers on record, the weather service said.

In the summer of 1976, Britons sweltered in one of the longest heatwaves in living memory, with 15 consecutive days hitting 32C or higher.

There was a significant drought with no rainfall recorded for 36 days across the whole of England and Wales between June and August that year.

The dwindling water supplies led to the passing of a Drought Act, water rationing and the use of standpipes.

In south-east Wales, conditions were so severe that supplies were cut off for 17 hours a day for up to 11 weeks, and 70 companies in the area were ordered to halve water consumption.

The harsh conditions took their toll on agriculture, with £500million worth of crops destroyed, resulting in soaring food prices.

Subsidence was also a problem as the ground became increasingly parched and insurance claims rose to £60million.

At the time, it was England and Wales's driest summer since records began in 1766.

The summer of 2018 is currently the second hottest on record, when a mean temperature of 15.76C was measured, followed by 2006, 2003 and 2022.

This year, England and Wales saw their warmest spring on record after a heatwave in May and six consecutive days where temperatures hit more than 30C.

Mr Partridge said climate change meant the extreme spells of weather were becoming 'more frequent'.

'That's unfortunately just the way things are going at the moment and it doesn't seem to be slowing down,' he said.

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.

'As 40+ temperatures become ever more common, expect many thousands sleeping in the streets as poorly insulated homes become uninhabitable heattraps, widespread power cuts as power cables sag and break, transport chaos as rails, overhead wires and signalling fail, and A & E departments overwhelmed by the old, very young, and vulnerable suffering from overheating.'

It comes four weeks after a record-breaking heatwave saw England and Wales record their hottest ever day in May with highs of 35.1C and 32.9C respectively. 

The Met Office has only issued extreme heat warnings three times before – in August 2022, July 2022 – when the UK reached its only ever 40C day - and July 2021.

Meanwhile, Europe is also sweltering under the heatwave, with temperatures forecast to hit 37C in Rome and 39C in Madrid this afternoon.

In France, highs of more than 40C are expected today as emergency services and military forces have been put on wildfire alert.

Public alcohol consumption restrictions have been put in place by French authorities and some outdoor sporting events cancelled.