Image source, PA Media

Brian Jordan, director of 999 operations at London Ambulance Service, says high temperatures can have a significant impact on health.

A busy day for the ambulance service would see 5,500 emergency calls but they are anticipating up 8,000 calls today, Jordan tells the BBC.

He says the public can help by staying safe and responsible by looking after themselves and others in the heat.

He advises the public to "only call 999 if it’s a genuine emergency - if it's urgent rather than an emergency, contact NHS 111 online for support, external".

Asked about how ambulances will manage if patients are having to wait long periods in outside hospitals in the heat before being admitted, he says a patient flow system is in place for crews to contact a control room to advise which hospitals are the least busy - and that ambulances are air conditioned.

Justin Rowlatt
BBC Climate editor

Image source, Getty Images

So why are we seeing such brutal temperatures? Most climate scientists say the answer is climate change.

Today’s heatwave is happening when average world temperatures have risen by just over 1C from their pre-industrial levels.

One degree doesn’t sound much, does it? But we’re living in the hottest period for 125,000 years, according to the UN’s climate science body, the Intergovernmental Panel on Climate Change.

We know what’s behind this - greenhouse gas emissions caused by our burning of fossil fuels like coal and gas. Concentrations of CO2 in the atmosphere are at the highest level for two million years, according to the IPCC. And they are increasing.

Remember that big UN conference in Glasgow last year? Well, if all the promises governments made there are actually implemented then we’re looking at temperatures rising by 2.4C from pre-industrial levels by the end of the century.

But the bad news is that emissions of CO2 continue to increase. Without big cuts very soon – and I mean by 2030 – we could see temperatures go even higher. Perhaps as much as 4C by the end of the century, according to the UN scientists.

What does that mean? I think you know the answer to that. It means more frequent and intense heatwaves like this.

As we've been reporting, a heatwave is sweeping across Europe and is now beginning to affect the UK.

A red extreme heat warning has been issued by the Met Office for parts of England, with temperatures set to hit as high as 40C (104F) this week. People are also being warned the hot weather could put their health at risk.

But why is it so hot? BBC Weather presenter Matt Taylor explains in the clip above.

Image source, PA Media

A cabinet minister has defended the government's level of preparation for extreme weather events, saying the UK isn't "stopping - we're adapting".

Asked if he agreed with health officials who've warned that thousands could die in this heatwave, Kit Malthouse, chancellor of the Duchy of Lancaster, didn't give BBC Radio 4's Today programme an answer. Instead, he says "lessons must be learnt" from previous heatwaves and those classed as vulnerable should take extra caution.

Despite various newspapers claiming the weather has brought Britain to a "halt" - with guidance for people to stay home and to avoid travel - Malthouse says the UK is "adapting" as best it can.

Pushed on whether "last minute Cobra meetings" suggests the government is really prepared for extreme weather events, Malthouse admits there are things - like the way buildings are constructed in the UK - that must evolve to take climate change into consideration.

Image source, Getty Images

No law in the UK says a given temperature is too hot or cold to work.

But workplaces should ideally be at least 16C, or 13C if the job is mostly physical - according to the Health and Safety Executive (HSE).

Its guidance says a workplace temperature must be "reasonable", external with "clean and fresh air".

A number of MPs recently backed a campaign for a legal upper limit of 30C in most workplaces, external - or 27C for those doing strenuous work - but the government doesn't have to respond.

Earlier this week, a Tower of London beefeater told us how he's been keeping ice under his hat to try and keep cool.

Read more about workers' rights in hot weather here.

Sadiq Khan - the mayor of London - has been tweeting advice for Londoners to stay safe during the heatwave.

He advises people to "only use public transport if your journey is absolutely necessary" and look out for each other, especially those less able to protect themselves, in "dangerous" hot weather.

Khan also urges Londoners who don't have to travel to work to "work where they feel most comfortable".

"For many this will mean staying at home, while others may prefer to go to office spaces which may be cooler and air conditioned."

Image source, NETWORK RAIL

Jake Kelly, leading the management of Network Rail's disruption today, says railway infrastructure will be under "exceptional stress" and advised all customers to check their train is running before they travel.

"The advice, very strongly, to customers in England and Wales is to only travel if it's absolutely essential and expect a very reduced train service and delays," he tells the BBC.

"Our railway is made up of lots of components, many of them metal, which expand in the heat.

"We do lots of work to prepare for the heat, including painting the metal white rails so they reflect the heat, and spending hundreds of millions a year on making the railway more resilient - but faced with weather like never before, it will suffer."

He says the East Coast Main Line route won't be running on Tuesday from London to destinations like Peterborough, Leeds and York.

Network Rail plans to run a full service from Wednesday but that "depends on the damage the weather does to the infrastructure over the next few days," he says.

Image source, Getty Images

As the heat goes up, so does the risk to animals’ health. Battersea Dogs and Cats Home’s welfare manager Rebecca Verne gave BBC Breakfast some tips to keep your dog cool during a heatwave:

• Remember you don’t have to walk your dog in the heat – on days like today, focus on mental stimulation rather than physical exercise
• Use anything at your disposal – paddling pools, hoses, buckets and cans – to keep your dog cool
• Freeze your dog’s food by popping it in the freezer– it will cool them down as they eat it
• Watch out for signs of heatstroke in dogs: the signs are similar to heatstroke in humans and include symptoms like vomiting, diarrhoea, behavioural changes such as confusion and disorientation. If you spot any of these, call your vet

Georgina Rannard
BBC News

Yes, Britain has been slowly getting warmer since the 19th Century. In the past three decades, the UK has become 0.9C warmer.

The 10 hottest years since 1884 have all happened since 2002. And none of the coldest years has been recorded this century.

Climate change is causing global temperatures to rise.

Greenhouse gases, like carbon dioxide, released into Earth's atmosphere in large volumes are trapping the sun's heat, causing the planet to warm.

Periods of intense heat do occur within natural weather patterns, but scientists say, external they are becoming more frequent, more intense and are lasting longer as a result of global warming.

That trend is predicted to continue. It's possible that by 2100, the UK could see 40C days every 3 to 4 years, external.

Image source, .

Image source, Getty Images

Demand for water is currently "at a near-record level", says Andrew Tucker - a water demand reduction manager for Thames Water.

Speaking to BBC Radio 4's Today programme this morning, he said the hot weather has led to "everyone wanting more" water and "mostly at the same time".

Tucker says Thames Water aren't currently expecting to introduce restrictions on water but "that situation might change" if it doesn't rain in coming months.

He urged people not to waste water and said "with everyone playing their bit, we'll get through this".

Charity Waterwise has some tips to save water here., external

A Met Office red warning for heat, external came into force at midnight across large parts of England, stretching from York and Manchester to London and the south-east. Here's a look at what the warning means:

• Population-wide adverse health effects, not limited to those most vulnerable to extreme heat, leading to serious illness or danger to life
• Substantial changes in working practices and daily routines will be needed
• A high risk of failure of heat-sensitive equipment, potentially leading to localised loss of power and other essential services such as water and mobile phone services
• More people visiting coastal areas, lakes and rivers, with increased safety risks
• Delays, closures and cancellations for road, rail and air travel

Image source, Reuters

Anyone travelling today, whether by rail or road, is being warned they could face quite a bit of disruption.

Network Rail and Transport for London have warned people to travel only if necessary on Monday and Tuesday, with cancellations and speed restrictions in force on many lines.

Those who do travel are advised to wear cool clothes, take handheld fans and ensure they have plenty of water.

Some rail tracks have been painted white so they absorb less heat and rail workers use a method called "stressing" to prevent railway lines from bending.

Motoring organisation RAC is advising people to make journeys only if you have to and outside the hottest parts of the day - especially if you have an older car. If you do drive, keep an eye on the engine temperature as well.

Councils across England have got gritters on standby ready to spread sand, not salt, to try and stop the tarmac from melting.

Image source, The Metro / Daily Express

This week's extreme heat dominates Monday's front pages.

The Mirror carries the headline "Blowtorch Britain", alongside pictures of people enjoying the weather on the beach in Brighton on Sunday.

However, the paper reports that people are being warned to stay indoors on Monday and Tuesday amid "death fears and travel chaos".

The Metro's front page has dubbed today "Meltdown Monday" and reports that temperatures are set to top 40C.

"Hotter than the Sahara" is the Sun's heatwave headline, with the paper reporting that temperatures in Britain are set to top those in India, Pakistan, Algeria and Ethiopia.

The Guardian says that passengers have been urged not to travel by train today but that the deputy prime minister has said schools shouldn't close due to the heat.

The Telegraph's lead says there is a 60% chance of temperatures reaching 40C, while people are being urged to get their "40C winks" and take siestas during the heat wave, reports the Star.

More here

Image source, PA Media

On Sunday, temperatures exceeded 30C (86F) across England and Wales, with a high of 33C in Hawarden in Flintshire making it both Wales's and the UK's hottest day of the year so far.

The highest temperature in England on Sunday was 32C in Nantwich, Cheshire, while Scotland saw a high of 26.4C at Auchincruive in Ayrshire.

Northern Ireland also had its hottest day of the year so far, with 27.7C recorded in Armagh.

An official heatwave in the UK is when at least three consecutive days have daily maximum temperatures meeting or exceeding the heatwave temperature threshold.

But the threshold varies between 25C and 28C depending on the part of the country.

The threshold was raised by 1C in some areas earlier this year.

• A red extreme heat warning has come into force for the first time in the UK - covering a swathe of England including London, Manchester and York on Monday and Tuesday
• It’s the Met Office’s highest weather warning - meaning a risk to life, travel disruption and potential loss of power or even mobile phone signal.
• That would be the highest temperature ever recorded in the UK, above the current high of 38.7C set in Cambridge in 2019
• Amber warnings cover the rest of England, as well as all of Wales and southern Scotland
• A number of schools are closing and others are ditching uniforms
• Water companies have warned some households were experiencing lower water pressure and supply problems because of increased demand
• Network Rail and Transport for London have urged people to only travel if essential, while the RAC is telling people not to travel during the heat of the day

Thanks for joining us on this Monday morning, as a red heat warning covering a large part of England has come into force for the first time.

Other parts of the country are also facing a very hot day ahead, with amber warnings covering Wales and the south of Scotland.

We’ll keep you updated on the forecasts, news on disruption, official advice, tips on how you can safe in the heat and the broader context about this extreme weather that we face.

Stay with us - and keep cool.