The Health Impacts of Extreme Heat: Findings from our analysis for the Climate Change Committee

In 2024, the Climate Change Committee set out to develop the Well-Adapted UK report, one of the most significant assessments of climate adaptation the UK has seen. Bringing together leading researchers and economists across more than a dozen workstreams, it examined the risks posed by climate change across health, infrastructure, the built environment, land, nature and food.

Edge Health, alongside Greencroft Economics, were asked to lead one workstream within this, assessing the impact of extreme heat on health. Over the past year, we modelled those impacts across the 2030s and 2050s under varying warming scenarios. The Well-Adapted UK report, including this review, was published on 20 May. You can read the full report here and our detailed heat and health report here.

This is the first of a two-part series. Here, we explore the health impacts of extreme heat. In part two, we look at how adaptation could reduce these adverse impacts.

Following England’s warmest June on record, summer 2025 went on to become the hottest since records began in 1884. As we explored in our previous blog on Why Climate Change is a Public Health Crisis, these heatwaves signal growing risks to public health and to health services across the UK.

Yet the UK is not adapting fast enough to mitigate these risks. The Climate Change Committee’s assessment of the most recent National Adaptation Programme found that progress has been slow across the board. Below, we share some of the key findings from our workstream on what this means for people and the NHS.

By 2050, heat-related deaths could be eight times higher than today

Heat affects the body in several ways. As temperatures rise, the body works harder to maintain a safe internal temperature, mainly through sweating and increased blood flow to the skin. In extreme conditions, this system can become overwhelmed, raising the risk of dehydration, heat exhaustion, and heatstroke.

Our analysis consisted of developing a simulation model to understand the impact of extreme heat on health outcomes in the UK population, specifically due to the present-day¹ and projected temperatures in the future (2030s and 2050s). We found that even in the present-day scenario, extreme heat² was already taking a significant toll on health in the UK. On average, there were 4.9 days of extreme heat per year, associated with approximately 850 excess deaths, 17,000 excess A&E attendances, and 2,900 excess emergency admissions annually.

To put that in context, the economic costs of these heat-related health impacts at present-day scenario is roughly equivalent to 80% of the annual economic burden of seasonal influenza.

These figures are set to rise sharply. Under a central climate scenario of around 2°C of global warming by 2050, the UK would experience more than twice as many days of extreme heat per year, leading to a near three-fold increase in heat-person-days when accounting for projected population growth. The health consequences are stark:

• Deaths are projected to rise from around 850 per year in the baseline to 2,200 by the 2030s and 3,200 by the 2050s. In a worst-case scenario of 2.5°C warming, this could reach 7,400 deaths annually – more than eight times the baseline level.
• A&E attendances are expected to climb to 39,000 by the 2030s and 53,000 by the 2050s under the central scenario. In a worst-case 2050s heat year, this could surge to 123,000 attendances nationally, with London alone exceeding 27,000 – nearly seven times its present baseline.
• Emergency admissions are projected to rise from 2,900 in the baseline to 7,250 by the 2030s and 11,000 by the 2050s, reaching 26,000 in the worst-case scenario.

In total, the monetised health impacts of extreme heat could exceed £4 billion per year by the 2050s in the worst-case scenario.

The burden of extreme heat falls unevenly

Extreme heat does not affect everyone equally in the UK. The largest absolute impacts are concentrated in London and Southern England, due to higher number of extreme heat occurrences and older population. In the 2050s worst-case scenario, the South East alone accounts for around 27% of the total UK heat-related mortality.

Vulnerability also varies sharply across populations. People aged 75 and over are most at risk, experiencing heat-related mortality at around eight times the rate of other age groups, with emergency admissions similarly concentrated in this group, reflecting the higher prevalence of chronic conditions and age-related frailty worsened by heat stress. By contrast, A&E attendances are disproportionately concentrated among younger adults – partly reflecting health-seeking behaviour, such as parents bringing young children to emergency departments. This highlights how extreme heat could create distinct pressures across different parts of the health system.

Heatwaves disrupt the NHS’s ability to deliver care, while driving more demand for services

As more people become unwell, healthcare demand rises, adding extra pressure to an NHS that is already stretched. Research has shown that on a day of 25°C, 999 calls increase by 20%, placing pressure on emergency response and acute care.

But it’s not just demand that increases; heat can also disrupt the NHS’s ability to deliver care. In the 2022 heatwave, 1 in 5 doctors reported cancellations of surgeries in hospitals, likely due to overheating in clinical spaces. Our analysis of the Estates Returns Information Collection found that overheating incidents in NHS estates reached nearly ~7,000 in 2022/23, more than double the number in 2016/17.  

This is coupled with the impact on healthcare staff’s health and wellbeing. A survey found that 20% of healthcare professionals took time off during the 2022 heatwave, averaging 2.2 days due to symptoms of heat stress.

Based on our work modelling demand and capacity across the NHS, we know this pressure doesn’t stop in summer. Disruptions to planned care, staffing capacity, and resource allocation could create knock-on effects stretching into winter, when the system is already under pressure.

These findings paint a clear picture: extreme heat is already a public health challenge, and without action, it will become a far greater one. But our modelling shows that targeted action could significantly reduce that toll. In part two, we explore what an effective adaptation response looks like and how those measures should be prioritised.

1. The present-day baseline represents the average temperature profiles over the period 1991-2020. ↩︎
2. Extreme heat is defined as temperatures above defined heat threshold of 25°C or more at LSOA or data zone level, following the UK Met Office approach to derive meteorological thresholds for heat waves. Note that this varies by region between 25-28°C, and when using LSOA thresholds by 25°C-29°C. ↩︎