Image source, Getty Images

With the hot weather comes the possibility of disruption to travel.

Today, a number of train lines are experiencing disruption after passengers in areas affected by the red warnings were asked to only travel if their journeys were essential.

Here's a look at the latest disruption:

On the trains

• Avanti West Coast is running fewer trains on some routes - with a reduction of one train per hour on Birmingham New Street, Manchester Piccadilly and Liverpool Lime Street routes
• The operator is also warning services running between Carlisle and Motherwell may be terminated at Preston
• Chiltern Railways are running reduced services on some of its routes while the CrossCountry network has cut some of its services including between Reading and York. There are also a number of cancellations on c2c services
• LNER has altered its timetable particularly affecting services to and from Leeds and to and from Lincoln
• Meanwhile, on the West Midlands Railway and London Northwestern Railway, trains are not running between Leamington Spa and Nuneaton - following a rail buckling in the heat - or between Liverpool Lime Street and Crewe
• Transport for Wales is running fewer services on some routes, while those between Chester and Wrexham General, between Pontypridd and Cardiff Bay and between Shrewsbury and Birmingham International are among those that have been cancelled until the end of the day
• AndElizabeth line services are not able to call at terminals at Heathrow airport due to issues with infrastructure caused by the heat

Image source, Getty Images

On the Tubes and Overground

There are minor delays on the District Line due to hot weather mitigation - other London Underground lines including Central, Circle and Metropolitan are experiencing delays due to train cancellations.

While on the London Overground, the Mildmay and Suffragette lines are seeing severe delays following an earlier signal failure.

Hospitals in England say their facilities are being stretched and equipment is being impacted due to the extreme heat.

Services at two hospitals in Stafford, the Royal Stoke University Hospital and County Hospital, have been "unable to operate at normal capacity in the heat and humidity".

The high temperatures are affecting operating theatres, testing labs and MRI scanners, according to the NHS Trust which runs both hospitals.

Meanwhile, a spokesperson for St George’s University Hospitals NHS Foundation Trust, which runs two hospitals in south west London, told the BBC its facilities are also under “extra pressure” due to the heat.

“Our ageing buildings weren’t designed for these temperatures, but we are doing everything we can to keep people safe and comfortable,” they added.

Matt McGrath
Environment correspondent

Anna in London says 1.5C of warming compared to pre-industrial times doesn’t sound like much, but this heatwave is way warmer above normal than that. Can you explain how these two connect?

You raise a very interesting and often confusing issue, Anna.

The 1.5C figure refers to a global average of temperatures compared to what they were before the industrial period began in around 1850 - when we started burning fossil fuels and adding greenhouse gases to the atmosphere.

The figure includes day and night temperatures from all over the world, from mountains to oceans and everything in between.

Essentially it is a long-term measure of the whole Earth's fever, not a reading of any one day in any one place.

A heatwave like the one we’re experiencing is the opposite: one corner of the planet, on land, in high summer, at the hottest point of the day.

So the two numbers aren't measuring the same thing, and there's no reason they'd match.

But a brutal heatwave can run many degrees above what's normal for the season, precisely because small changes in the global average can have major effects on our local weather - as we are now seeing in the UK and Europe this week.

Image source, EPA/Shutterstock

Anglian Water is urging customers to use less water as increased usage puts pressure on the company's network.

On Wednesday, it put a record 1,600 million litres of water in supply, which is a third higher than its typical distribution of 1,200 million litres.

Ian Rule, director of water services, says Anglian Water has "no plans to introduce a hosepipe ban", but higher-than-usual water consumption can lead to issues "such as bursts and low pressure".

"We're having to produce more water than ever before to keep everyone on supply, so we'd urge customers to avoid using hosepipes and use less water wherever they can," he says in an update posted to the company's website.

Michelle Roberts
Health editor

There are lots of things that you can do to cope with the heat:

If you are outdoors, stay in the shade and wear light-coloured loose-fitting clothing, ideally made of cotton or linen that allow air flow and let sweat evaporate. Wear high protection sunscreen and apply it often.

Stay hydrated by drinking plenty of water - around six to eight glasses or more. Diluted squash, fruit juice and iced-tea or coffee also count.

Keep your home cool. Close windows, curtains and blinds during the day and open them at night when the temperature outside has gone down.

Turn off any lights or electrical equipment that you don't need as they can make your home feel hotter. Electric fans can help though.

Babies who breastfeed should get all the water they need from breast milk and don not need any extra, the NHS says - but they may want to feed more than normal.

And take things slowly. Don't rush or do anything too physical if you are hot.

If you or someone else feels unwell with a high temperature during hot weather, seek medical advice.

Wales has recorded its hottest ever June day with a provisional temperature of 34.2C recorded in Bute Park, Cardiff.

Previously, the highest temperature for Wales in June stood at 33.7C - recorded in 2000.

It comes after the record for the hottest June day in the UK has been broken again after Yeovilton in Somerset recorded a provisional temperature of 36.4C - higher then yesterday's 36.1C in Hampshire.

We're looking through the latest set of provisional temperatures as a heatwave continues to grip the UK, stay with us.

Esme Stallard
Senior climate and science reporter

Lornawants to know: when will the UK roll out air conditioning across all infrastructure - including schools and transport?

Data on the percentage of homes with air-conditioning in the UK is limited - previous government estimates, external have put it at single figures.

But it is fair to say it is not the norm in the UK. We’re used to average summer temperatures of 16C., external

The UK Climate Change Committee (CCC) - independent experts that advise the government on all things climate - has recently estimated that 22% of homes in the UK will need some sort of "active" cooling measure such as air-conditioning in the future as the world gets warmer.

This issue has been hotly debated in politics recently.

The Conservative Party said there is a de facto ban on air-conditioning in new homes under building regulations. That isn’t quite true.

The regulations call for developers to consider all passive options first - i.e. things that will bring down the temperature without you having to do anything. This is to limit the use of extra energy.

Passive measures includes things like proper insulation, shading on windows, and increased green space.

Regulations have also been updated recently to reduce the amount of glass in new buildings to try and stop temperatures becoming unbearable in offices and homes.

At the beginning of the 21st century, glass skyscrapers were springing up across our cities. But it has been accepted that this has increased the risk of overheating.

Image source, Getty Images

Paul Kirby
Europe digital editor

Image source, Getty Images

Heatwave conditions that have left Spain, France and the UK sweltering are set to shift to the east in the coming days.

Temperatures in Germany could hit 40C in some western and south-western areas today, and across the country on Friday.

An extreme weather warning is now in place in much of the Czech Republic.

In France, which recorded its hottest day on Wednesday, Prime Minister Sébastien Lecornu announced the health alert level is being raised to its highest, to boost hospital staffing and protect the vulnerable.

Much of northern and southern Switzerland was put on maximum weather alert by MeteoSuisse, which warned of a "significant drought situation".

Although temperatures in Spain are set to peak at 38-39C in some areas today, forecasters say a cooler mass of Atlantic air is coming in.

An amber heat warning will remain in effect until 21:00 GMT in parts of England on Saturday, before temperatures cool on Sunday.

Our panel of experts are answering your questions as a red extreme heat warning is extended to Friday for London and parts of south-east England.

You can follow along by clicking watch live at the top of this page.

Image source, Getty Images

The London Ambulance Service responded to the highest number of life-threatening emergencies in its history on Wednesday.

Temperatures soared to 36.1C in parts of the UK on Wednesday, and that record for June has been broken again today.

Ambulance crews responded to 642 calls relating to category 1 incidents - those that include the most serious, life-threatening injuries and illnesses such as cardiac arrests and patients who are not breathing.

Chief Executive Jason Killens KAM said this was "driven by the extreme heat across London".

Mark Poynting
Climate reporter

The widespread expectation is that 2027 will become the world’s hottest year on record.

Part of the reason is that a natural weather phenomenon called El Niño has begun in the Pacific Ocean.

These events tend to peak in strength around Christmas time and boost global temperatures into the following year.

And this El Niño will happen on a planet that is much hotter anyway because of human-caused climate change.

Matt McGrath
Environment correspondent

As we've just reported, the record for the hottest June day has been broken again.

Turning back to our climate experts, Bev in Dorset asks whether this hot spell will feel worse than 2022’s due to high humidity.

There are two aspects to this heatwave that are making it feel worse than previous hot spells - the air is unusually humid, and the nights are barely cooling down.

Humidity measures moisture in the air - the higher the level, the harder it is for us to cool down. Sweating works when it can evaporate from skin, this is made harder when the air is already laden with moisture.

The Dew Point - which is a gauge of how much water the air is holding - is an important number to consider.

The Met Office says it could reach around 22C on Wednesday and Thursday. During the record-breaking July 2022 heatwave, when the UK first passed 40C, Dew Points were only in single figures. The air then was bone dry.

The second factor is the lack of overnight relief. Across much of England and Wales, temperatures are not expected to fall below 20C at night - what forecasters call a tropical night.

Image source, EPA

The Somerset village of Yeovilton has recorded the highest June day temperature ever.

Across the UK, here's a look at the highest temperatures recorded in each UK nation.

The June records for Scotland, Northern Ireland and Wales were recorded in 1893, 1976 and 2000, respectively.

Today's record also only applies to June - the hottest temperature ever recorded in the UK was 40.3C in Coningsby, Lincolnshire, in July 2022.

Hazel Shearing
Education correspondent

At least 1,600 schools in England have experienced closures and disruption during this week’s heatwave. That’s on top of 840 in Wales.

The Department for Education doesn’t publish a list of schools that have closed during the heatwave, so the figure for England is only an estimate.

We’ve been looking at individual councils’ websites in areas most affected by the heatwave, and counted 1,691 that have fully or partially closed, or that have offered parents the option to pick their children up early.

The actual number is likely to be higher, not least because councils aren’t required to publish this data and some schools might not appear on their lists.

Most schools have stayed open, although academy trusts have reported lower attendance over the heatwave.

Earlier, Prime Minister Keir Starmer said "each school will gauge for themselves the measures that are appropriate".

Image source, Getty Images

We've just reported that the Met Office recorded a provisional temperature of 36.4C in Yeovilton - making it the hottest June day on record.

Here are the latest provisional temperatures across other parts of the UK, as of 14:00 BST:

• Otterbourne, Hampshire - 35C
• Wiggonholt, West Sussex - 34.3C
• Bournemouth Airport - 34C
• Boscombe Down, Wiltshire - 34C
• Bute Park, Cardiff - 33.3C

The Met Office has recorded a provisional temperature of 36.4C at Yeovilton, Somerset, making it the hottest June day on record.

This beats yesterday's hottest June temperature record of 36.1C in Hampshire, which broke the longstanding record from 1976.

Image source, Philbert Nut / BBC Weather Watchers

Helen Willetts
BBC Weather

A 'heat dome' has developed

At the centre of this is a large, slow‑moving area of high pressure that has effectively produced a "heat dome".

The high pressure causes air to sink, and as it sinks it compresses and warms.

At the same time, it suppresses cloud formation, allowing long hours of strong sunshine. Because the system is slow to move, heat builds up day after day and becomes trapped beneath this “lid” of stable air.

Strong summer sunshine

At this time of year, we have what’s called a "positive energy balance" - meaning more energy is coming in from the sun than is escaping back into space at night.

Under clear skies, that energy builds quickly, driving temperatures higher by day and with short nights, less energy is lost at night.

Hot air being drawn in from the south

The position of this high pressure is also key. It’s pulling up very warm air from southern Europe and beyond.

So we’re not just heating the air locally — we’re importing already hot air, where temperatures are also widely extreme and red warnings have been and are still in force. On Tuesday, France broke its all time temperature record, reaching 44.3C.

Dry ground intensifying the heat

Although there has been some recent rain, the ground has dried out rapidly.

That means less of the sun’s energy is being used to evaporate moisture, and more goes directly into heating the surface and the air above it — further boosting temperatures.

In short, the reason it's so hot is acombination of a persistent high pressure evolving into a heat‑trapping dome, strong sunshine, imported heat, and dry ground that’s driving this exceptional spell.

Helen Willetts
BBC Weather

Jamesgot in touch from "sweltering" Barwell in Leicestershire. He wants to know how the Met Office and BBC measure temperature.

All official UK air temperatures are measured in a standardised way which allows readings to be comparable across the country and over time.

Across the UK there is a network of Met Office weather stations where the air temperature along with other observations are recorded.

These thermometers live within a Stevenson screen to avoid direct heat. These boxes are painted white to reflect direct sun and louvred to ventilate.

In order to take a true air temperature, not a ground one, the screens sit 1.25m above the ground.

There are also strict rules about location, for example, not on concrete and away from buildings.

So when we say it’s 35C, that’s the standardised temperature not a reading influenced by direct sunshine or a hot surface.

Image source, Getty Images

Mark Poynting
Climate reporter

Rob, 28, says many people will blame this extreme weather on the El Niño weather pattern. Can you explain how climate change may be contributing to the extreme heat as well?

It’s a good question, but scientists aren’t blaming this heat on El Niño.

Let’s recap: El Niño is a natural weather phenomenon which develops when a change in wind patterns allows warmer waters to spread across the tropical Pacific Ocean. It happens every two to seven years, roughly.

Earlier this month, scientists declared that a new phase of El Niño had begun.

El Niño typically boosts global temperatures and can fuel heatwaves in South America, South East Asia and parts of Australia.

But there is no clear or consistent link between past El Niño events and summer heatwaves in the UK.

Instead, scientists are putting this week’s heat down to a combination of a strong high-pressure system and climate change.

• Prepare for El Niño, UN warns - it could be the strongest in decades

Justin Rowlatt
Climate editor

We have always had hot days and heatwaves. Climate change doesn’t create every hot spell from scratch. But it does change the odds.

Think about it. We don’t get that many days that are very hot or very cold. Most days are closer to average. Plot them on a graph and they look a bit like a bell, with the very hot and very cold days at either end.

Global temperature has increased by around 1.4C since pre-industrial times. That may not sound much. But now look at the second curve. The hot end has shifted quite a bit.

That means temperatures that used to be rare are now closer to normal - more days cross the line into extreme heat.

So heatwaves become more likely. And when they happen, they are more likely to be hotter and last longer, because they are happening in a world that is already warmer.