How Heatwaves Affect Your Business – and What to Do About It

What is a Heatwave?

A popular flavour of crisps….? a good day to go to the beach….? a hosepipe ban…? Heatwave is a word that we often hear but have you ever stopped to think about what the term means, and why we seem to be using it more often?

In the UK, the Met Office defines heatwaves differently depending on location. Broadly, 3 days of maximum temperatures exceeding 28^oC in wider London, 27^oC in the wider South-East, 26^oC in central and western areas and 25^oC everywhere else constitute heatwave conditions, which you can see in this map below:

Records Are Breaking – Here’s the Evidence

Last weekend in the South-West of the UK, where I live, temperatures topped a balmy 33^oC. This was off the back of three days with highs ranging from 27 to 30^oC. Firmly in heatwave territory.    

Recent analysis of UK weather records has found that the number of days with temperatures 5^oC above the average for 1961-1990 have doubled in the last 10 years. For days 8^oC above the number has tripled, and for 10^oC above it has quadrupled.

In short, heatwaves are becoming more common and hotter.

Why 1.5°C of Warming Feels Like 33°C on the Ground

When governments talk about things like Net-Zero, they often refer to numbers like 1.5 degrees or 2 degrees of warming. The difference between these numbers and what we experience in a heatwave is stark and can be confusing.

The reason for this is statistical. Government targets refer to average temperatures, and a heatwave is defined by maximum temperatures. In a normal distribution, a small shift in the mean will result in a much bigger change in the likelihood of extremes, and subsequently, extreme temperatures and heatwaves become much more common. The graph below shows how this can happen…

What Heatwaves Mean for the Way We Live

Why does this information matter?

A shift in maximum temperatures has big implications for how we live and how the country operates. Let’s have a look at a couple of examples from the rail industry and the NHS.

In the UK, rail is designed to have a stress-free temperature of 27 degrees (the mean UK summer temperature). As the track gets hot, it expands and wants to buckle; the hotter it gets, the more stress is placed on the sleepers and ballast that keep everything in place. Next time you’re on a train, have a look out the window and you might see certain sections of track painted white – a simple and hopefully effective way to keep temperatures down a bit. Hotter countries have functioning railways, but the summer-to-winter variations in the UK are a real challenge to our infrastructure. Concrete slab track bed can also be used to contain higher forces; however, Network Rail estimates that this approach costs approximately 4 times as much to install as standard ballasted track.

However, the impact of heatwaves is not limited to the material. Heatwaves have much more significant implications for human health and the functioning of the NHS. The London School of Hygiene and Tropical Medicine (LSHTM) estimated that around 570 people in England and Wales died as a result to heatwave conditions from the 19^th– 22^nd June 2025. Older people were expected to be hit the hardest, and people with underlying health conditions like diabetes, heart conditions and respiratory issues were most vulnerable. People living in more deprived areas are also considered to be more vulnerable. As quoted by Professor Antonio Gasparrini, lead of the EHM lab at the LSHTM, “Every fraction of a degree of warming will cause more hospital admissions and heat deaths, putting more strain on the NHS”.

The Business Cost of Heatwaves

From a business perspective, heat waves have also been shown to have negative impacts on employee productivity. Government research indicates that every degree of indoor heat above 26 degrees costs the UK economy £770 million annually from lost staff days.

What does this mean for you and your business? As heatwaves in the UK become not just more frequent but more intense, the ripple effects will be felt across society. Developing resilience in response to these changes is important, now, at all scales, from global supply chains to national infrastructure, and the welfare of your employees. Understanding where your business vulnerabilities are, and developing appropriate mitigation, will need to be an essential part of your future planning and success.

Contact Action Sustainability to find out more about how you can make your business more resilient to the impacts of climate change.