Image source, luke_8m

The ambulance service is trying to reach people stuck in traffic for hours on the M25 after a crash led to lane closures in the soaring heat.

Driver Kerry Matthews says she was stuck for five hours and had to turn her air-conditioning off to save petrol - she was left feeling "very wobbly" by the time she made it to the petrol station, BBC South East reports.

In a Facebook post, another woman says her parents have been stuck "for over 4.5 hours" without information or supplies.

She says there are "elderly people, babies, animals, [and] people with health conditions" stuck on the tarmac on "the hottest June day for 50 years".

She adds: "Can the police not coordinate some water and assistance? The exits are taking hours".

Another posted that her parents in their 70s had seen ambulances trying to get through and people "lying on the ground unwell".

Image source, Getty Images

Queen Alexandra Hospital in Portsmouth has declared a critical incident after a cooling system supporting "critical infrastructure" failed during the heatwave.

Mark Orchard, deputy chief executive and chief financial officer of Portsmouth Hospitals University NHS Trust, says: “The unprecedented pressures created by the current heatwave, combined with the failure of a number of our chiller units, have led to significant disruption across several of our services."

He says services impacted include "digital systems and critical clinical services, including theatres, cardiac catheter laboratories, and diagnostic scanning facilities".

Some planned procedures and appointments have been "stood down", a statement from the hospital says - those impacted have been contacted already.

Patients are warned the hospital is "very hot" so to limit the number of people accompanying them to appointments.

Today's temperature has surpassed the previous June record set in 1976 of 35.6C.

It comes weeks after May saw its hottest day on record, when temperatures reached 35.1C.

BBC Weather presenter Simon King explains why this is significant and warns it will likely get hotter in the coming days.

Lola Schroer
BBC News, reporting from Richmond

James O'Mara-Roberts, who works at the boat cafe Peggy Jean in Richmond, London, says today has been long one.

"It's the hottest day I've ever worked," he tells us.

Customers "are a bit more stressed" than usual but have generally remained patient, though their choice of drinks have changed.

He adds: “Customers have been wanting cold drinks, a few spritzes and a lot of cocktails. Coffees have been scarce."

Forecasters not exaggerating heat in 'dark red’ mapspublished at 19:46 BST

19:46 BST

By Marco Silva

Social media posts claiming weather maps are making UK heat look worse than it is are misleading.

Deep red colours are commonly used by weather forecasters to show high temperatures, but some posts previously seen by BBC Verify have wrongly suggested they are meant to exaggerate weather and scare people.

Forecasters say the colours simply reflect how hot it actually is, including both the Met Office and BBC Weather who have updated their graphics in recent years.

Temperature maps use a standard colour scale: cooler conditions appear in blues, while higher temperatures are shown in progressively darker reds.

These changes were made to ensure consistency and improve accessibility - for example, by making it easier for people who have trouble distinguishing colours to read a weather map.

The Met Office says the UK’s June temperature record, 35.6C, set in Southampton in 1976 and Camden Square in 1957, is likely to be broken this week.

When maps appear more intense it is because the temperatures themselves are unusually high. The colours used are not exaggerating the heat, they are accurately representing it.

Image source, Met Office

Wednesday

Amber and red alerts for extreme heat came into effect at 09:00 this morning, covering much of England and Wales.

Thursday

The same alerts will come to an end at 23:59 BST. A yellow alert for thunderstorms has also been issued for the south-west of England, lasting from 18:00 to 23:59.

Friday

A separate amber alert for extreme heat, lasting from midnight on Friday until 23:59 covers south-east England, eastern England and parts of the Midlands.

Saturday

An amber alert for extreme heat will be in place from midnight on Saturday until 21:00. It covers a smaller part of England, including London, the south-east, and east of England.

Image source, Met Office

Is the world losing the climate battle?

Former US Secretary of State and US Climate Envoy John Kerry says "no" - but tells BBC News: "But we're not yet winning."

The former presidential candidate says the world is experiencing incredible heatwaves and droughts around the world, and that every decade for the last four has been hotter than the last.

Speaking in the BBC's London's newsroom, he says: "You would think at some point people who are supposed to be reasonable, and leaders, would stop and say 'OK, enough, we've got to respond to this'."

On the US specifically, Kerry, a Democrat, criticises Defence Secretary Pete Hegseth and President Donald Trump, who he calls "dangerous and reckless" on their approach to the climate.

Other countries are turning to new technologies to slow down climate change, in areas like fuel and electric vehicles.

"Really amazing things are happening," Kerry adds.

Even King Charles III was feeling the heat today as he attended a London Climate Week reception at St James's Palace.

Master of the Household to the Sovereign, Vice Admiral Sir Tony Johnstone-Burt, was close by and armed with a battery-powered fan to assist.

Image source, PA Media

Hugh Schofield
Paris correspondent

For the second day in a row France has recorded its hottest day since measurements began after World War Two.

The average temperature over Wednesday based on readings at 30 weather stations around the country was 30C. Tuesday had already set a record with 29.9 degrees.

The temperature in Paris and many other areas broke 40C on Wednesday.

On Thursday, 72 departments or counties will be in the maximum red alert zone. This is the largest area to be in the red zone since the system was developed. Only the southeast of the country is relatively spared.

Two departments – Haute-Garonne in the south and Deux-Sèvres in the west – are also on maximum alert for forest fires.

The heatwave is slowly shifting to the east but no immediate relief is expected, with temperatures above 40 forecast for the weekend.

Image source, Reuben Brown

Several people stranded in traffic on the M25 after a crash earlier are being treated for heat-related illnesses, South East Coast Ambulance Service says.

Lanes were closed on a stretch of the motorway in Surrey, with drivers stuck on the road for "several hours" as temperatures soared.

The ambulance service says coach passengers are among those being treated, without specifying how many people are unwell.

Heavy traffic means ambulances are still trying to reach people on the road near Godstone.

A driver was airlifted to hospital earlier today after a van and lorry were involved in a serious crash.

A "significant oil spillage" damaged the road, police said earlier.

Passengers are being warned to avoid non-essential travel - but if you do need to make journeys in the hot weather, here are some tips:

• Carry water with you and stay hydrated. Water fountains are available at some stations - ask staff if you need help locating one.
• Check journeys before setting off for delays or cancellations. A number of operators have reported disruption and limited services.
• Wear light, cool clothing and consider having a handheld fan.
• Don't forget to charge up any essential devices, as power supplies could be impacted too.
• If you feel unwell, do not travel - and seek assistance from staff if you become sick during your journey.

Barra Best
BBC News NI weather presenter

Northern Ireland is officially in the grip of a heatwave, but thankfully a much cooler one.

For the third day in a row the temperature dial has hit 25C, this time in Castlederg in County Tyrone.

The heat is expected to peak tomorrow though, rising close to a more uncomfortable 30C in some parts.

That would come close to Northern Ireland’s highest temperature on record, which is 31.3C set in July 2021.

It'll be a similar story in the Republic of Ireland where a record almost 140 years old could be threatened - 33.3C was recorded at Kilkenny Castle on 26 June 1887.

The Irish weather service, Met Éireann, issued a yellow heat warning from noon on Tuesday until 09:00 on Friday.

In England, a new UK June record was hit today in Gosport, Hampshire, with 36.1C.

In Wales, the mercury has hit 33.3C in Cardiff Bute Park, topping yesterday's maximum for the nation.

Scotland's highest temperature has been 27C in Charterhall, while Northern Ireland has seen 25.5C in Castlederg. Though neither have experienced temperatures as high as Tuesday, when they both recorded their hottest days of the year so far.

Image source, BBC Weather Watchers/@KWR

Charlotte Hadfield
Live reporter

This was the scene at London Euston at rush hour this evening as hundreds of people try to get home in the baking heat.

Trains to Liverpool Lime Street, Manchester Piccadilly, Crewe, Northampton and Bletchley are among the services cancelled due to the hot weather, while others are facing long delays.

Several platforms are closed and people are using handheld fans to try and cool down, while others are sitting on the floor clutching bottles of water.

I’m travelling to Stockport on the delayed 16:53 Avanti West Coast train, which has just departed.

People in front of me were running to try and get a seat on the train.

Thankfully, I’ve found one and the air conditioning is working, but those sitting in coach D are not so lucky.

Commuters are facing widespread transport disruptions due to the hot weather. People are being advised to check their routes before travelling. Here's a list of what's affected:

• In London, severe delays are reported on some Tube lines, including: Victoria Line, Northern Line, Lioness Line and parts of the Bakerloo, Central and District Lines
• The M25 in Kent and Surrey is closed after two vehicles were involved in a serious crash
• Transport for Wales has cancelled services across Wales due to extreme heat and a shortage of trains. The rail operator says some routes will remain out of action until the end of the day
• London North Eastern Railway has told customers to not travel unless it's "absolutely necessary. Disruptions have also been reported by a number of train operators

A major rescue operation is under way after a 15-year-old boy went missing after swimming at a nature reserve.

Emergency services have been attending the scene at Testwood Lakes, near Totton, Hampshire, after the teenager was reported missing at 13:35 BST.

Hampshire Police says it has deployed marine units to aid in the search, with people advised to avoid the area.

The National Police Air Service, South Central Ambulance Service, and Hampshire and Isle of Wight Fire Service have also been sent to the scene.

The June heat record keeps getting pushed higher. The maximum recorded now is a provisional 36.1C in Gosport, Hampshire.

Esme Stallard
Senior climate and science reporter

Image source, Just Farms/Ceri Squire

For those whose livelihoods are dependent on the weather conditions, these repeated heatwaves throw up challenges.

Ceri Squire, a sheep and cattle farmer in Bridgend, says: "The unusual weather means that the seasons, as my in-laws used to farm by, are no longer consistent periods of months. We have to be flexible."

She says that she is having to spray her sheep down regularly to prevent blowflies taking hold and laying eggs in the wool.

Ceri adds: "This week we were planning to take livestock to a local livestock market, but we are legally not allowed to transport animals in temperatures over 30 degrees unless we have a temperature controlled vehicle for them."

For many smaller family-run farms, they are too expensive to have.

This week the National Farmers' Union urged the government to do more to tackle the "stark" impacts of climate change, saying "fields that produce wheat for the nation’s bread can be underwater one year, then parched and cracking the next".

Alex Meakin

The Hurst School in Berkshire is one of many across the county that have closed early today to shield pupils from the warm weather.

A little earlier, headteacher Jayne McLaren told us: “The first most and important thing to me is always the wellbeing of my staff and students.

"The temperatures in some of the class rooms are in the high thirties now and we haven’t got the highest temperatures yet.

“We’ve had many trips to the medical centre. We have children that are suffering with heat exhaustion. It is difficult for us to keep them safe here.”

She said that she hoped things are "back to normal" next week, adding: "The temperature looks like it's coming down to the early 20s which, compared to now, is tolerable."