Commuters in London have been advised not to use the city's transport network unless for "essential journeys," amid a sweltering heat wave across western Europe.

The UK Met Office issued an amber extreme heat warning from Sunday through Tuesday as temperatures will likely surpass the country's 2019 record temperature of 38.7 Celsius (101.7 degrees Fahrenheit), posing a risk to passengers.

“Due to the exceptionally hot weather that is expected next week, customers should only use London's transport network for essential journeys,” Transport for London (TfL) chief operating officer Andy Lord said.

Temporary speed restrictions will be introduced to London's tube and rail services “to keep everyone safe,” Lord added, urging travelers to “carry water at all times.”

Searingly hot temperatures can damage power lines and signaling equipment. TfL has said it will try to keep services running smoothly and use increased inspections to alleviate the impact of extreme heat.

Regular track temperature checks will take place to prevent tracks from bending or buckling, TfL said in a statement. The network will also check air conditioning units across the Tube network and air cooling systems on the capital's double-decker buses.

Motorists have also been encouraged not to drive during the hottest spells of the day.

‘Lives are at risk’

The UK Met Office has said people's lives are at risk as temperatures could reach 40C early next week.

It issued its first ever red extreme heat warning for parts of the country including London and Manchester, calling the alert “a very serious situation.”

“If people have vulnerable relatives or neighbours, now is the time to make sure they're putting suitable measures in place to be able to cope with the heat because if the forecast is as we think it will be in the red warning area, then people's lives are at risk,” Met Office spokesman Grahame Madge said.

The UK Health Security Agency also increased its heat health warning from tier three to tier four — the equivalent of a “national emergency.”

Wildfires ravage Spain, France and Portugal

Elsewhere in Europe, wildfires ravaged parts of Spain, France and Portugal Friday in the blistering heat, burning forests and prompting widespread evacuations.

Over 400 people were evacuated from Mijas, a picturesque village in Malaga, southern Spain as a new wildfire erupted, Reuters reported. About 20 kilometers (12.4 miles) away, beachgoers in Torremolinos spotted smoke billowing near coastal hotels. Authorities in Catalonia suspended sports and camping activities in about 275 towns and villages to prevent fire hazards.

Flames have also engulfed parts of Extremadura in western Spain, as well as the central Castille and Leon region. The wildfires threaten historical landmarks including a 16th century monastery and a national park, while over 18,500 acres of forest have been destroyed.

Water-bomber aircraft and over 1,000 firefighters have been deployed in southwestern France to contain two blazes exacerbated by strong winds and tinderbox conditions, Reuters reported. Elsewhere 11,300 people have been evacuated since wildfires exploded near Dune du Pilat and Landiras, where about 18,000 acres of land has been burnt.

Temperatures were expected to exceed 40C in Portugal, where five districts were on a red extreme heat alert and more than 1,000 firefighters confronted 17 wildfires, according to authorities.

There was a spike in heat wave-related casualties in western Europe. Portugal recorded 238 excess deaths from July 7 to 13, according to the country's DGS health authority. Spain registered 84 excess deaths in the first three days of the heat wave, the National Epidemiology Centre's database said.

Climate crisis pushes extreme weather

Scenes of firefighters tackling wildfires and roads melting in extreme heat may look dystopian, but UK forecasters say these phenomena are a result of the ongoing climate crisis.

In the summer of 2020 meteorologists at the UK Met Office used climate projections to predict the weather forecast for July 23, 2050 — and the results are startlingly similar to their forecast for Monday and Tuesday.

“Today, the forecast for Tuesday is shockingly almost identical for large parts of the country,” Simon Lee, an atmospheric scientist at Columbia University in New York, tweeted Friday, adding in a later post that “what is coming on Tuesday gives an insight into the future.”

“We hoped we wouldn't get to this situation,” the Met Office's climate attribution scientist Nikos Christidis said in a statement. “Climate change has already influenced the likelihood of temperature extremes in the UK. The chances of seeing 40°C days in the UK could be as much as 10 times more likely in the current climate than under a natural climate unaffected by human influence.”

The chance of exceeding 40 degrees is “increasing rapidly,” Christidis said.