A new University of Oxford–led study, published in The Lancet Planetary Health, provides the first comprehensive evidence linking daily temperature variation to health-care use and costs across both primary and secondary care in England. By combining detailed weather data with large-scale patient records, the research offers a system-wide picture of how everyday exposure to heat and cold translates into demand for NHS services, moving beyond earlier studies that focused on specific conditions or parts of the health system.

The analysis draws on linked records from 4,366,981 people registered at 244 GP practices between April 2007 and June 2019. Using these data, the researchers examined how health-care use changed when average daily temperatures fell outside a mild reference range of 18°C to 21°C. They estimate that exposure to temperatures outside this range accounts for about 3.0% of the recorded health-care costs in their dataset. This figure reflects the cumulative effect of many small increases in service use on non-optimal temperature days, rather than the impact of rare extreme events alone.

To illustrate the possible scale of these findings, the study presents an indicative translation into national spending terms. If a similar proportion applied to NHS England’s planned 2023/24 spending on acute services, specialised services and primary medical care — a combined £101.4 billion — temperature-related health-care use would correspond to costs on the order of £3 billion per year across those categories. While this is not a formal national budget estimate, it provides context, placing temperature-related costs in the same broad range as established areas of NHS expenditure, such as dentistry.

The results are particularly relevant as NHS leaders plan for winter pressures and wider service resilience. Cold weather remains a dominant feature of the UK climate, with days averaging between 0°C and 9°C accounting for around 64.4% of the estimated temperature-related burden. This reflects sustained increases in health-care use across the winter period rather than sharp peaks on individual days. The study also identifies a practical concern during periods of extreme cold: when average temperatures fell below 0°C, recorded health-care use declined, suggesting that hazardous conditions such as snow and ice may create barriers to accessing care, even when health needs are likely to be high.

At the same time, the study highlights growing risks associated with hot weather, which is becoming more frequent under climate change. Very hot days were rare during the study period, limiting precision. Still, the data show clear same-day surges in parts of the system, including accident and emergency attendances and prescribing, when temperatures are unusually high. These rapid increases can place immediate strain on services and challenge day-to-day delivery.

Overall, the findings point to a key contrast: cold weather is linked to a larger cumulative burden on the NHS, while heat is associated with sudden spikes in demand. Older adults were consistently the most affected group across the analysis. The study suggests that planning for temperature-related variation in health-care use should be treated as a year-round issue, requiring attention to both recurring winter pressures and emerging heat-related risks.

More information: Patrick Fahr et al, Quantifying the health-care burden of temperature in the National Health Service in England: an economic analysis of resource use and costs, The Lancet Planetary Health. DOI: 10.1016/j.lanplh.2025.101373

Journal information: The Lancet Planetary Health Provided by University of Oxford