UK heatwave: What happens when the country reaches 40C?

Forecasters say there is a higher-than-average chance of heatwaves in the second half of July

Sun, sea and sand are images we usually tend to associate with summer, but over the past few years that has changed, now pictures of scorched earth and dried-up reservoirs have become increasingly commonplace as the climate crisis comes into sharper focus.

As the planet continues to warm, scientists say extreme weather events are becoming more frequent and on 19 July last year, during a sweltering heatwave, the mercury hit a staggering 40.3C in Coningsby, Lincolnshire – the hottest ever temperature recorded in the UK.

Large parts of the country have seen plenty of sunshine and high temperatures over the past month, following a wet and dreary start to the year.

And it looks as though more baking hot weather is on the way.

Forecasters say there is a “greater than normal” chance of heatwaves in the second half of July, following the warmest June on record.

High-pressure conditions are set to create a “correspondingly higher likelihood” of a heatwave, sparking fears that the temperature record could be broken just a year after it was set.

Wildfires

Professor Richard Betts, who heads the Climate Impacts Research at the Met Office, said the impact of temperatures of 40C on the UK’s animals species was “uncharted territory”.

“The main point for the UK is that 40C is not something that species in this country are adapted to because it is virtually unprecedented – no creatures or plants in this country experienced temperatures of 40C until the 19 July last year, so it’s uncharted territory,” he told The Independent.

“Since we expect these temperatures to happen more often now as a result of climate change, species will increasingly be experiencing temperatures to which they are not adapted. What this means in detail remains to be seen, but in principle, a shift outside of a species’ climate niche poses a threat.”

He added that one of the more visible impacts of the extreme temperatures were the wildfire that raged in parts of the UK last year.

“[Wildfires are] something that the UK is not prepared for, and in particular, British people are not accustomed to being careful not to risk starting fires in hot weather. So until/unless people can become more careful about fire risk, we can expect fires to continue to occur when we get extreme hot weather.”

Drought

July last year was the driest in England since 1911 and droughts were declared in several areas across the country the following month, including in Bristol, Somerset, Dorset, south Gloucestershire, parts of Wiltshire, Devon, Cornwall and the Isles of Scilly.

Hosepipe bans were issued in several areas, including Wessex where public and businesses were advised to “use water wisely as the dry summer impacts the environment”.

An Environment Agency report found this year found that monthly rainfall totals for the majority of river catchments were classed as “exceptionally low” for the time of year.

In August, there had been five consecutive months of below average rainfall across all geographic regions in England and above average temperatures.

With Wessex now officially in drought, 11 of the 14 Environment Agency areas in England are now in drought status.

There are four classifications the agency uses to manage arid conditions across these areas. They are: prolonged dry weather, drought, severe drought and recovering drought.

Melting roads

As well as having a negative impact on animals, plants and water systems, higher-than-average temperatures can also create havoc in everyday life, sometimes causing travel disruption and extremely uncomfortable conditions on public transport.

The UK’s motorways and major A roads are highly resilient to extreme weather and “approximately 94 per cent of the network has an asphalt surface which can withstand high temperatures,” National Highways (NH) says.

Soaring temperatures

• 50C – temperature at which tarmac starts to soften
• 70C – temperature needed to cook an egg

There is also a small percentage of roads in the country that have concrete surfaces, which are unaffected by heat. Both types of road surface are suitable for use in very hot weather and in a changing climate.

“The design and build standards we apply ensure our roads are kept safe and serviceable,” NH adds.

“Our design standards are considered best practice and have been adopted by other countries around the world.”

During last year’s heatwave in July, sky-high temperatures affected some roads that were not resilient against extreme conditions.

Part of a road in, Blyton, Lincolnshire, melted as the surface temperature exceeded 54C.

There was a similar report in Stockport, Greater Manchester, where the top layer of Broadstone Road buckled under the heat.

Tarmac viscoelastic material, which means that as a solid it’s very strong but it can also transition back to a liquid under intense heat. At around 50C, the material softens and melts, although this only tends to affect the top layer.

A road in the UK melts amid scorching hot temperatures (PA)

Residents of London will be all too familiar with the suffocating heat on the city’s packed Tube trains during the warm weather. Because a lot of the network is underground,  this – along with the heat generated from the trains – means temperatures are regularly a few degrees above those on the ground.

Just how hot can it get? The Evening Standard newspaper said it recorded a temperature of 47C on the Central Line in July 2006 during a heatwave that gripped the entire continent of Europe.

Fast forward to 2023 and Transport for London (TfL) says there are now 192 air-conditioned Tube trains covering 40 per cent of the network, with enhanced tunnel ventilation systems on the Victoria and Jubilee lines.

TfL says that, with heatwaves becoming more common, it has a “comprehensive” hot weather plan in place to keep services running.

“We’re also working hard with our partners to explore how we better adapt to, and prepare for, the impacts of climate change and ensure that our transport services are more resilient in the face of more extreme and frequent weather events,” Carl Eddleston TfL’s network management and resilience director, said.

“When high temperatures arise we encourage customers to carry water with them when they travel, to look out for each other while travelling, and use TfL’s real-time travel tools, including status updates, Journey Planner and TfL Go, for the latest information on how TfL services are operating.”