Britain is in the grip of its second red extreme heat warning of 2026, and for Torolf Hamm, managing director and global head of physical risks in the Climate Practice at WTW, the signal is unmistakable. He noted that a conference on heat stress in London recently had to be cancelled because of the heat.
The Met Office issued a red extreme heat warning for parts of England and Wales on June 24 and 25, with temperatures reaching 37.3°C. The second official heatwave of the year followed a record-breaking spell in May that saw 35.1°C recorded at Kew Gardens, surpassing a record that had stood since 1922.
Hamm's central argument is that businesses are still treating extreme heat as a weather story rather than a structural risk shift.
"You can't treat it like a weather event," he said. "It's systemic. It will happen year on year again. Starting to work with this new status quo of volatility is perhaps where there needs to be more education and understanding of what climate change means."
He draws on personal experience to make the point. Living in Whitstable, Kent, he recently found himself without running water when local infrastructure buckled under tourist demand and development that the network had not been designed to accommodate. Nearby areas experienced similar disruption again this week.
"This is not a one-off anymore," he said. "What are we doing about it? There needs to be investment, but it needs to be targeted."
The risk for managers, he argues, is also psychological.
"In the past perhaps there was a perception that something materially impacting your business was a 1-in-30 type event. What we're seeing now is that this is almost very likely to happen within the timeframe of you managing the risk. You will experience it."
Insurance Business UK has tracked how heat-related losses are reshaping underwriting appetite, with insurers applying higher subsidence excesses, tighter acceptance criteria and, in some cases, natural peril exclusions. The British Geological Survey has projected that properties exposed to shrink-swell subsidence risk could rise from 3% in 1990 to nearly 11% by 2070.
Hamm sees the challenge as broader than property. Rail networks, water infrastructure and public health services are operating to standards designed for conditions that no longer exist.
"You need to look at your design standards, your building standards, how we're measuring some of those things," he said. "We can learn a lot from countries already exposed to these risks because at the moment we don't."
He points to railways as one example. Whether track temperature is measured using ambient air temperature or directly on the rail surface matters because the threshold or way of measurement used to trigger operational changes may itself be outdated. The same logic applies across infrastructure: standards calibrated for a previous climate are quietly becoming obsolete.
For risk managers advising corporate clients on climate exposure, Hamm's advice is practical and immediate.
"Start to engage with your supply chains. Look at what you could do before, during and after an event. Make sure you have preferred suppliers who give you first access to repairs so that you are not suffering when there is demand surge."
He is equally direct on the role of brokers.
"Link to your brokers and insurers and make sure you are putting them on alert. The brokers should probably do the same, making clients aware that we have heightened weather patterns and that some events are likely."
As the Prudential Regulation Authority's (PRA) General Insurance Stress Test, launched in May 2026, presses firms on climate-driven property exposure, Hamm warns that the probability calculus has fundamentally shifted. What catastrophe models once treated as a one-in-100-year event may now be closer to a one-in-10 or one-in-five occurrence, meaning businesses still planning around historic return periods are already behind.
"You are actually very likely to experience it," he said. "And you need to start to finance your risk - transfer, investment into adaptation, making sure that you understand your vulnerability."
The window for treating extreme heat as an exceptional event has closed.
"We are already living in a 1.5-degree world," he said. "Imagine what it will look like living in a 3-to-4-degree world. It will be awful, and that is the call to arms."
