Climate change is often talked about in terms of emissions targets and future scenarios, but most people experience it far more directly: through overheated homes, disrupted travel, worsening air quality, rising food costs, and strained health services.
The evidence is clear. The UK's weather is becoming warmer and wetter, and adverse weather events - heatwaves, flooding, extreme cold - are growing more frequent and intense. The last decade has been warmer than any previous decade on record, and summers we once considered exceptional are becoming the norm. Summer 2026 has already broken records with a new maximum temperature record for June.
We have now seen UK temperatures exceed 40°C. In a climate unaffected by human activity, this would be extremely unlikely. Climate change is already making heatwaves more frequent, longer-lasting, and more severe - and the health consequences are serious. Without concerted action to adapt our communities and health and social care, these trends will only continue to worsen.
What are the health risks of hot weather?
Not everyone copes equally well as temperatures rise. In the UK, excess heat-related deaths begin to occur above 25°C, with risks rising sharply as temperatures climb further. At 27°C and above, people with under-developed or impaired sweating mechanisms - including very young children, older people, and those with long-term health conditions or taking certain medications - find it especially difficult to keep cool.
Heat exacerbates cardiovascular and respiratory conditions and increases the risk of sudden, serious events such as heart attacks, strokes, and breathing difficulties. Crucially, the impacts on mortality are felt quickly - often within 24 hours of the onset of high temperatures.
In 2025 UKHSA experts were involved in a study that assessed the role of socio-environmental factors in heat-related deaths. The study noted that these risks are not felt equally across society. Two people can experience the same temperature very differently depending on their housing, access to green space, working conditions, and wider social circumstances. Climate resilience is not just an environmental challenge - it is deeply bound up with inequality and wellbeing.
What happened during summer 2025?
Last summer was the warmest UK summer on record, with 5 separate heat episodes. An estimated 1,504 heat-associated deaths were recorded in 2025 - around 1,535 fewer than the modelled estimate based on historical temperature-mortality relationships, a consistent pattern across every heat episode. While data from 2025 provides early evidence that heat resilience may be improving, there is more work to do, particularly to protect vulnerable older populations.
In 2023, UKHSA and its partners implemented an updated Adverse Weather and Health Plan for England, supporting local and national organisations in preparing for and responding to heatwaves. The same year, UKHSA launched a new impact-based Weather-Health Alerting system to provide early warning when adverse temperatures are likely to impact health and wellbeing. Actions taken across health, social care, and emergency response sectors, alongside protective behaviours in the wider population, all contribute to improving heat preparedness and resilience. It demonstrates that with the right planning and public awareness, lives can be saved even during record-breaking heat.
How can we protect communities during heatwaves?
The harm caused by extreme heat is not inevitable. There are steps individuals, communities, and organisations can take both year-round and during periods of adverse weather to reduce risks.
Our most important call to action during any heatwave is simple: look out for those who may struggle to cope, particularly older people, young children, and those with long-term health conditions. Our guidance also sets out practical advice tor staying safe during hot weather.
When heat poses a significant risk, UKHSA and the Met Office issue Heat-Health Alerts (HHA). A red HHA - first issued in 2022 and again in summer 2026 - indicates a risk to life even among healthy people, and signals that heat could disrupt not only health and care services but also transport, energy, water, and food systems.
Heat can affect vulnerable populations even during yellow HHAs, however. While a yellow HHA may not reflect ‘extreme’ heat, we do see mortality during these periods among vulnerable, often older, populations. Yet many people don’t recognise the risk that these temperatures can pose or the need to protect vulnerable friends, family, colleagues, and neighbours.
You can subscribe to email Weather-Health Alerts on the UKHSA website.
What is UKHSA doing about climate and health in the longer term?
Globally, climate change is one of the greatest threats to health security, with potential impacts on air quality, food and water availability, infectious disease risk, and mental health and wellbeing. UKHSA's Centre for Climate and Health Security provides scientific advice and support to ensure these impacts are considered in cross-government policy across local and national government, the NHS, and internationally.
Our landmark Health Effects of Climate Change report is an evidence–based assessment of the range of health risks and brings together the latest UK climate change projections.
By monitoring the health effects of our changing climate and risks due to extreme and adverse weather, and providing robust guidance, UKHSA is working to ensure that communities across England are better protected - now and in the years ahead.