Emergency services have been called out across England today in response to heat-related incidents. Here is a reminder:

Hampshire: A major rescue operation was launched after a 15-year-old boy went missing after swimming at Testwood Lakes nature reserve.

Hampshire Police said it deployed marine units to aid in the search and the police air service, ambulance service and fire services were also sent to the scene.

Surrey: The ambulance service said more than 10 people were taken to hospital, primarily for minor heat-related illnesses, after being stuck on the M25 motorway in Surrey after it closed due to a crash.

Drivers were stranded in lanes of traffic for several hours. Earlier in the day, a driver was airlifted to hospital after a van and lorry were involved in a serious crash.

Portsmouth: A critical incident was declared at Queen Alexandra Hospitalafter a cooling system supporting "critical infrastructure" failed partly due to the pressures of the heatwave.

Systems impacted included digital systems, critical clinical services and diagnostic scanning facilities.

We can bring you more now on the accident on the M25 that has left drivers stranded in the heat for hours.

The South East Coast Ambulance Service says more than 10 people have been hospitalised, "primarily with minor and heat-related" conditions after being stuck in traffic.

Crews have now left the scene after assessing and treating a number of patients, the ambulance service adds.

It's not just the UK that is suffering from a heatwave - many other parts of Europe are also sweltering.

The temperatures continue to cause deaths and disruption, particularly in France, Spain and Italy.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

The UK has seen its hottest June day on record, with 36.1C recorded in Gosport in Hampshire.

The place may be a far cry from the sandy shores of The Bahamas, but its highs make it hotter than the Caribbean country of The Bahamas, which reached 31C on Wednesday.

Here's where else the Hampshire town - known for its shingle and pebble beaches - is hotter than:

• New York - 29C
• Barbados - 30C
• Madagascar - 30C
• Barcelona - 30C
• Costa Rica - 31C

• Jamaica - 33C

Temperature in other parts of Europe, however, are sweltering as a heatwave grips the continent. In Bordeaux, France, and Bilbao in Spain, temperatures hit 42C.

Galya Dimitrova
BBC South of England

Image source, Submitted

Thirty-one passengers have been evacuated from a hovercraft in the south of England after its engines were seen smoking.

Hovertravel's Island Flyer was preparing to depart from Southsea, Portsmouth to Ryde on the Isle of Wight when a fire warning was activated, the company says.

Fire crews attended the scene and the pilot used the onboard fire extinguisher.

The company says its services are currently cancelled and will next give an update at 06:00 on Thursday.

• Read more on this story here

In warm weather, it can be harder to sleep as bedrooms become stuffy and hot.

As bedtime approaches, here are some tips and tricks to help you have a peaceful rest:

An MP has taken to social media to ask emergency services to help drivers that have been stuck on the M25 for hours.

Folkestone and Hythe MP Tony Vaughan addressed National Highways and Surrey Police in a post on X, writing: "Please sort this out urgently.

"People need water and some may need evacuation. You have protocols for this situation - please implement them - this is an emergency!"

He says one constituent had been stuck on the motorway near Oxted with her children for eight hours and that her car was 40C.

"She is running out of water. The person from the car in front has been airlifted to hospital with dehydration. Police seem to be saying it's not their job to give out water," Vaughan adds.

Earlier, we reported that the ambulance service is trying to reach people stuck on the M25 after a crash led to road closures.

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 co-ordinate 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.