UK heatwave July 2025

With the UK experiencing another heatwave over the next few days, we take a look at the effects it can have on rail and buildings.

Rail

John Lawrence, Chair of our Railway Technical Network said: “Heat is a significant issue for the railway, affecting infrastructure and trains alike.

The management of it is a cross-industry whole year exercise fitting into the seasonal preparation activities done by maintenance teams and planners across the network. The most noticeable areas affected by heat are also the ones causing the most significant disruption.

Ambient temperature and solar gain combine to create very high temperatures at track level and in equipment location cases trackside. Track buckles and dewirements are the most significant thing that keep engineers up at night – even with the amount of focus, investment and improvements made in recent years, situations still arise where rails buckle in the heat.

This can lead to potential derailment risks and overhead lines can sag and snag on the pantographs of trains leading to train movements stopping, or being rerouted for a significant period of time.

“There are also hidden failures, too. Much equipment on the railway can suffer heat stress, with signalling control, power supplies and telecoms systems trackside particularly affected, switch-creep caused by rail expansion at points can affect detection and stop trains being routed across them, so where the passenger may see signalling failure, this could very well be caused by overtemperature somewhere on the network. Lineside fires can also be a problem, maybe caused by discarded rubbish, sparks from steam locomotives or maintenance trains, causing significant disruption, whether they arise on the infrastructure or even in a lineside neighbour's premises.

“Managing these issues is costly and time consuming and with the greater prevalence of high temperatures, it is becoming more of a hazard over time. You may notice rails being painted white to reflect solar gain at specific risk points on the network, improved tensioning equipment on overhead line gantries to managed dynamic tension, fresh ballast dropped to hold rails in position and rail joints lubricated to enable expansion.

“What you may not see as a passenger, however, is the hidden technology and processes monitoring condition and taking action to provide early warning of failure. Such as, short, medium and long-term weather reporting to give planners a chance to react.

"Rail stressing to maintain equal tension for expansion and contraction. Vision systems monitoring pantograph contact, yellow trains on the network monitoring dynamic track stability, critical rail temperature sensors providing warning of danger or signalling systems and points being monitored for a range of defects that can affect operation.

"You might also be surprised to find thermal imaging drones and helicopters monitoring equipment for overheating and visual inspection and defect correction taking place overnight.

“Temperature management is a huge issue for the railway and the focus of much research, development and activity across the season. But with the changing climate, it is an ever-present issue for the day-to-day operation of the railway.”

One of the key ways that networks prevent tracks from overheating is by painting them white.

Dr John Easton, who’s also part of our Railway Technical Network, added: “This can reduce the track temperature by 5°C and reduces signalling failures which lead to significant disruption. 

“This technique is also used in countries where high temperatures are more commonplace, such as Italy, where engineers often paint the inside faces of the rails white to reflect the sunlight and lower the risk of buckling.”

Hot homes and buildings

Anni Feng, one of our built environment experts and a member of our Digital Futures Policy Centre said: “When it’s really hot outside, many of us feel uncomfortable indoors too. That’s not just because of the building itself, but also because of what’s around it.

“Think of it like this: buildings don’t stand alone. The materials used in roads and nearby buildings can trap heat, making the whole area hotter. This extra heat can make people try to cool things down with fans or turn up air conditioning units.

“But if too many people do that at once, the local energy system might struggle to keep up. That can lead to problems like cooling systems not working properly, which could even affect things like computers and other equipment inside buildings.

“Achieving climate resilience in the built environment requires holistic, systems thinking. It demands a broad approach to understand how buildings, people and the wider environment interact, and to design for future climate conditions while working towards integrated, long-term solutions.

“When considering how we adapt for hotter temperatures, we should ask the questions like what this might mean for surrounding buildings, the environment and people in the communities – both short term and long term – and are they contributing positively to the future we aspire to create.”