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Feeling the heat: the challenge of rising temperatures in prisons

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In the last three months the UK has experienced record-breaking temperatures, high humidity and frequent severe weather warnings. But what happens when lots of people are locked up together in these conditions, with limited access to fresh air and ways to keep cool? Inspector Rachel Badman explores how intense and prolonged heatwaves are affecting prisons and the people who live and work in them.

Undertaking inspections over recent months has, at times, been uncomfortable. Sitting around a table in a hot, stuffy meeting room for hours, walking around the top landing of an already warm prison wing, or standing in direct sunlight in an unshaded exercise yard have made jails a challenging place to be, and that’s without the heavy uniform or protective equipment that prison officers have to wear. Most prisoners have little control over their environment or access to things that might make the heat more bearable.

Much of the prison estate is outdated and ill-equipped to cope with sustained high temperatures. Prison design has understandably prioritised security, with many establishments featuring thick stone walls, limited ventilation and restricted access to outdoor space. Rising prisoner numbers means 24% of prisoners now live in overcrowded accommodation. In some prisons, up to 300 prisoners share a single wing across several landings, with those on upper landings particularly exposed to rising heat and direct sunlight through skylights.

The Ministry of Justice (MoJ) has recognised that climate change poses growing risks to the prison estate. Many prisons and young offender institutions already overheat during summer months and this is likely to get worse in the future. To understand why this matters, it is important to consider the conditions in which many prisoners already live.

In some jails, more than 70% of prisoners share a cell designed for one person. These cells can be extremely cramped, often leaving little room for furniture and forcing prisoners to eat meals while sitting on their beds. Food can remain in cells overnight, worsening smells and attracting vermin.

Many cell windows either do not open properly or provide little airflow, and measures introduced to combat drones, including secure windows, restrictors and external grilles, can further reduce ventilation. We often find cells without curtains to block sunlight and, at one recent inspection, discovered hot pipes running through already overheated accommodation. These conditions affect comfort, sleep and well-being.

In many cells, toilets sit directly beside the bed, and screening is absent or improvised using towels or sheets. We continue to encounter blocked toilets and, in some establishments, prisoners still rely on lidded buckets because cells lack in-cell sanitation and running water. During inspections we have seen prisoners throw urine and excrement from cell windows rather than store it in their cells, sometimes splashing into cells below and creating both a health and decency concern. This only adds to the unpleasant odours in prisons, with hot weather likely to intensify the problem.

Prisoners can spend up to 23 hours a day locked in stifling cells, with restricted access to the open air, showers and cold water. Many prisoners do not have freely available drinking water due to the lack of in-cell sanitation. Although prisoners are able to purchase fans, they are often not available or too expensive. At one prison, fans were only permitted for those sharing double cells.

Although high temperatures in prisons can affect healthy individuals, the impact is likely to be exacerbated for those with underlying conditions, including elderly prisoners (the numbers of whom are increasing), those with mental ill-health and those with alcohol and drug dependencies.

High temperatures in prisons are not simply a matter of health and decency; they also raise concerns about safety and order. Ministry of Justice analysis found that in the 12 months from January to December 2022, prisoners in overcrowded cells were 19% more likely to be involved in an assault[1] compared with those in non-overcrowded cells[2]. Research from the United States has also associated higher temperatures with increases in prison violence[3]. We have recently seen incidents linked to cell conditions, and there is a risk that increasingly hot and overcrowded environments could contribute to greater frustration and instability. This not only affects other prisoners but puts staff at risk.

As temperatures continue to rise and overcrowding remains acute, overheating in prisons is no longer simply an issue of comfort. It has implications for decency, health, safety and the stability of the prison estate. The prison service will need to consider how to mitigate these risks, as prisons remain overcrowded and become increasingly hot.

[1] This includes prisoner-on-prisoner assaults and assaults on staff.

[2] Ministry of Justice (2025). The impact of overcrowding on assaults in adult public prisons. https://www.gov.uk/government/publications/the-impact-of-overcrowding-on-assaults-in-adult-public-prisons

[3] Mukherjee, A. and Sanders, N. (2021). The casual effect of heat on violence: social implications of unmitigated heat among the incarcerated. National Bureau of Economic Research. https://www.nber.org/system/files/working_papers/w28987/w28987.pdf