Executive summary
Warm summer days in England that were historically considered benign are increasingly posing a health risk as a result of climate change. World Weather Attribution analysis shows that rising average temperatures have shifted the baseline climate, meaning that temperatures once associated with low risk now contribute to excess illness and mortality. The findings underline that heat-related health impacts are no longer confined to extreme heatwaves but are emerging during increasingly common warm conditions.
What happened
During the summer of 2025, England experienced several periods of sustained warm weather rather than a single, exceptional heatwave. Daytime temperatures frequently exceeded levels historically associated with increased health risk, while warm nights reduced opportunities for recovery.
Health services reported increased pressure during these periods, with higher rates of heat-related illness, particularly among older people, those with pre-existing health conditions and individuals living in poorly ventilated or insulated housing.
What the attribution analysis found
World Weather Attribution finds that human-caused climate change has increased the frequency of warm summer days in England and raised baseline temperatures. As a result, conditions that would previously have been considered typical summer weather are now occurring in a warmer context that elevates health risk.
The analysis shows that the likelihood of warm days exceeding health-relevant thresholds has increased substantially compared with a pre-industrial climate. This shift means that heat-related health impacts are now occurring more often, even in the absence of record-breaking temperatures.
Because temperature trends are well understood and closely linked to global warming, confidence in the attribution findings is high.
Implications for public health
A key finding of the study is that health impacts are emerging below traditional heatwave thresholds. Public health systems and warning frameworks designed around extreme events may therefore underestimate the cumulative impact of frequent warm days.
Housing quality, urban heat island effects and socio-economic factors further shape vulnerability, with disadvantaged populations facing higher exposure and lower adaptive capacity.
How climate attribution fits into health risk reporting
Climate attribution provides evidence linking rising temperatures directly to health outcomes. By showing how climate change shifts temperature distributions, attribution supports a reassessment of health risk thresholds and planning assumptions.
This is particularly important in regions like England, where populations and infrastructure have historically been adapted to cooler conditions.
Why this matters for organisations
For public health authorities, employers, insurers and local governments, the findings indicate that heat-related risk is broader and more persistent than previously assumed. Workforce productivity, healthcare demand and service delivery are increasingly affected by conditions that fall short of extreme heatwaves.
How to use this in your own risk work
Organisations should review heat-health action plans to account for cumulative impacts of warm days, update occupational heat thresholds and incorporate climate-adjusted temperature distributions into planning. Improving housing ventilation, urban cooling and public awareness will be essential to reducing health impacts as warming continues.
Source
World Weather Attribution (2025). Climate change turns warm summer days in England into a health threat.