Heat, health and inequality

Climate change is often described as a ‘threat multiplier’ – compounding existing societal inequalities.

In the UK, rising temperatures and more frequent heatwaves are already causing serious health, social and economic impacts; but these impacts are not felt equally. They are experienced disproportionately by people in more deprived areas who face greater barriers to coping with increased heat.

Heat is a growing risk in the UK

The UK is already experiencing hotter summers and more intense heatwaves. During the record-breaking summer of 2022, when temperatures surpassed 40°C for the first time in the UK, there were an estimated 2,985 excess deaths associated with 5 heat episodes.

Public health evidence shows that extreme heat increases the risk of:

dehydration cardiovascular stress respiratory illness premature death, particularly among older people and those with underlying health conditions

Crucially, vulnerability to heat is shaped not just by age or biology, but also by social and economic conditions, many of which are captured by deprivation indices.

The Climate Change Committee, in its recent A Well-Adapted UK report, has proposed that ‘by 2050, excess heat-related mortality should be no greater, and ideally lower, than today’s annual average’. Meeting this target will require not only reducing overall heat risk but addressing the unequal distribution of vulnerability across society.

Poor quality housing and exposure to overheating

One of the most important drivers of heat vulnerability is housing. People in more deprived areas are more likely to live in homes that:

are poorly insulated or poorly ventilated trap heat due to their building design (such as small flats with limited airflow) lack shading, green surroundings or external space cannot be easily adapted, for example with external shutters, loft insulation or passive cooling An important driver of heat vulnerability is housing. Credit: Unsplash.

UK housing stock is widely recognised as ill prepared for hot weather. In 2019, the Climate Change Committee warned that ‘UK homes are not fit for the future’. More recently, the English Housing Survey 2023 to 2024 found that 2.9 million households (12% of all households) reported that their homes get uncomfortably hot, highlighting the scale of overheating risk across the existing housing stock.

Evidence from overheating studies in London and other cities shows that indoor temperatures in some homes can exceed outdoor temperatures by many degrees, especially overnight. For low income households, the ability to reduce this risk is limited: renters often cannot make structural changes, and energy costs can make electric cooling unaffordable.

Urban heat and green space

Many of the UK’s most deprived communities are located in dense urban areas with limited green space. These areas are subject to the ‘urban heat island’ effect, where concrete, roads and rooftops absorb and re emit heat, raising ambient temperatures, particularly overnight.

Access to green and shaded areas is important in mitigating heat exposure, yet deprived neighbourhoods typically have less of both, alongside poorer air quality. This produces higher baseline temperatures, compounding the health risks already associated with poor housing conditions.

Where heat and deprivation overlap

GAD analysis shows that while heat-related climate risk and social deprivation do not always fully align, there are locations where they are concentrated.

Under a 4°C global warming scenario, climate projections indicate a substantial increase in the annual number of Hot Summer Days1 (defined as days where the maximum temperature exceeds 30°C) across large parts of England, with particular high exposure in the South East and major urban areas such as London2.

When mapped alongside the Index of Multiple Deprivation (IMD) (20253) at neighbourhood (Lower Layer Super Output Areas (LSOA)) level for England, it becomes evident that there are several areas with high level of deprivation (low IMD scores) that are also expected to experience a greater number of Hot Summer Days.

All the neighbourhoods that fall within both the 10% most deprived in England and the 10% highest exposure to Hot Summer Days are located in London boroughs.

Peterborough, Milton Keynes, Southampton, Bedford, Oxford and Worcester also have neighbourhoods with high levels of deprivation and a significant expected number of Hot Summer Days under a 4°C scenario.

While exposure alone does not determine impact, the co location of high heat risk and high deprivation points to a clear case for targeting of climate adaptation policy in these areas.

Health, disability and compounding vulnerabilities

Deprivation is strongly associated with poorer health outcomes, including higher rates of long term illness, disability and mental health conditions. People with existing health conditions tend to have greater sensitivity to extreme heat. For example, cardiovascular disease, respiratory illness and certain medications all reduce the body’s ability to regulate temperature.

When rising temperatures interact with these existing health inequalities, the result is not just higher discomfort, but higher morbidity and mortality during extreme heat events.

Limited financial and social capacity to adapt

Coping with extreme heat often requires resources: money, time, space and social support. Those in deprived circumstances are less likely to have:

access to private transport or cool public spaces flexible working arrangements that allow them to avoid heat savings to absorb higher energy bills during hot periods strong local services able to provide targeted support during heatwaves

Public health research shows that interventions relying on individual behaviour change, such as advice to keep cool or reduce exposure, are less effective when people have limited capacity to act on that advice. In this way, adaptation measures that are not explicitly equity focused can inadvertently widen inequalities.

Climate change as an inequality issue

This evidence shows that rising temperatures expose and intensify existing inequalities. Heat disproportionately affects those with the least capacity to adapt, recover or avoid harm.

This has direct implications for policy, particularly local policy. Climate adaptation cannot be treated as a neutral, technical exercise. Measures such as urban greening, housing retrofit, heat resilient design standards and targeted public health responses need to be prioritised in the most deprived areas. Many of these measures are delivered through local authorities and hence effective adaptation will depend not only on national strategy, but on place-based policy that reflects local patterns of heat exposure, deprivation and vulnerability.

As heat risk increases, adaptation policy that explicitly targets inequality is essential both to protecting public health and to ensuring that climate change does not deepen existing social divides.

This blog post is part of GAD’s ongoing research on climate and health. If you found it interesting and would like to learn more about our work in this area, please get in touch with us at climate.change@gad.gov.uk.

For geospatial information on heat, health and inequality, Climate Just is a free tool developed by The University of Manchester alongside additional contributors.

Disclaimer

The views expressed are the author’s own and the opinions in this blog post are not intended to provide specific advice. For our full disclaimer, please see the About this blog page.

While the Hot Summer Days metric captures the most extreme heat exposure, health impacts can occur at lower temperatures, particularly for vulnerable populations. As a result, it should be interpreted as an indicator of relative exposure to extreme heat rather than a full measure of heat-related health risk. ↩︎The analysis focuses on the projected absolute number of Hot Summer Days, which highlights areas of highest exposure. However, in some locations the relative increase in hot days compared to historical conditions may be more pronounced, which could present significant adaptation challenges even where absolute levels remain lower. ↩︎IMD data used here reflects socioeconomic conditions as of 2025 rather than future projections. While patterns of deprivation are likely to evolve over time, present-day data provides a useful indication of where vulnerability may currently be concentrated. ↩︎

https://actuaries.blog.gov.uk/2026/06/09/heat-health-and-inequality/

seen at 15:33, 9 June in Actuaries in government.