Research and analysis

Interim heat mortality monitoring report, England: May and June 2026

Published 30 July 2026

Applies to England

Main points

During the May and June 2026 heat events:

• there were an estimated total of 2,877 heat-associated deaths
• an estimated 753 heat-associated deaths occurred during the May heat episode
• an estimated 2,124 heat-associated deaths occurred during the June heat episode
• the mortality burden is already close to the highest annual totals previously recorded by UKHSA

What you need to know about this report

This interim report focuses on total heat-associated mortality estimates for the May and June 2026 heat episodes.

Detailed demographic, geographic and cause-specific analyses, and comparisons with UKHSA modelled estimates, are outside the scope of this publication.

Final figures of heat-associated deaths during heat episodes in 2026 will be published early in 2027.

Reason for this interim report

The UK Health Security Agency (UKHSA) produces the annual heat mortality monitoring report. These are official statistics that provide estimates of heat-associated mortality during heat episodes in England. These estimates support understanding of the public health impacts of hot weather and inform future preparedness and response activities.

During summer 2026, England experienced 2 notable heat events, one in May and the other in June, both of which were exceptional for different reasons. The May heat event occurred unusually early in the season, with record-breaking temperatures following a period of unseasonably cool weather. The June event was characterised by its intensity and formed part of a broader period of sustained hot weather across Europe. Given the public health significance of these events, and the considerable interest from policymakers, partners and the public, UKHSA has produced this interim report to provide an early assessment of heat-associated mortality. Such early assessments will only be undertaken following extraordinary periods of heat and would not normally be produced for routine heat events.

Although this report has been produced using the same data sources, analytical methods and quality assurance processes as the annual heat mortality monitoring report, the estimates should be regarded as preliminary and operational in nature. At the time of analysis, mortality data remains incomplete because of routine delays in death registration. Also, estimates for the June heat event are subject to additional uncertainty due to limited availability of non-heat period days for baseline comparison. The definitive assessment of mortality associated with these events will be published in the annual official statistics report in early 2027.

This interim report focuses on headline estimates of heat-associated mortality. Detailed breakdowns by age, sex, geography, place of death and cause of death are not included because the analysis is based on provisional death registration data that has been adjusted for reporting delays. Registration delays can vary between population groups, causes of death and geographical areas, and applying appropriate delay corrections across all breakdowns would introduce additional complexity and uncertainty into the estimates. In addition, this report does not include comparisons between observed heat-associated mortality and UKHSA modelled mortality estimates. These assessments require more comprehensive analysis and are therefore reserved for the annual publication. More detailed analyses will be provided in the annual official statistics publication once more complete mortality data is available.

The estimates presented in this report are therefore expected to differ from final numbers as additional death registrations are received and processed in the annual heat mortality monitoring report.  

Heat episodes

A heat episode is defined as days when the mean Central England Temperature (CET) is at least 20 degrees Celsius (°C) (see Glossary). One day either side is also included. This is the same definition as was used in the 2025 heat mortality monitoring report.

In reports on summers before 2025, a different definition was used taking account of heat health alerts (HHAs) issued. See Data sources and methodology for more information.

Within this report we will focus on 2 heat episodes, the May event (E1) and the June event (E2).

Episode 1 (E1)

The May heat episode lasted 4 days (24 to 27 May 2026). During this period, the Central England Temperature (CET) reached 21.8°C on 25 May and 23.2°C on 26 May. However, the wider period of warm weather was more prolonged, and the associated HHA picture was complex. Temperatures began to increase from 22 May and remained elevated until 28 May.

Episode 2 (E2)

The June heat episode lasted 8 days (21 to 28 June 2026). During this period, CET reached or exceeded 20°C between 22 and 27 June. As with the May event, the alerting picture extended beyond the period captured by the heat episode definition.

Observed heat-associated mortality

Overall findings

Using the UKHSA heat mortality monitoring methodology, an estimated 2,877 (95% CI: 2,476 to 3,278) heat-associated deaths were observed across the 2 heat episodes that occurred during May and June 2026 in England.

The May heat episode lasted 4 days and was associated with an estimated 753 heat-associated deaths (95% CI: 529 to 977), equivalent to an average of approximately 188 heat-associated deaths per heat period day. Daily deaths over this period peaked during hottest day of the period, the 26 May where CET reached 23.2°C.

The June heat episode lasted 8 days and was associated with an estimated 2,124 heat-associated deaths (95% CI: 1,758 to 2,491), equivalent to an average of approximately 266 heat-associated deaths per heat period day. As in May, the number of deaths peaked on the hottest day of the heat episode, 26 June where CET reached 26.5°C.

Figure 1. Daily deaths and daily mean temperature, England, May and June 2026

Further insights and contextual information

Interpretation of mortality estimates 

The estimated 2,877 heat-associated deaths observed across the May and June heat episodes represent a substantial public health impact occurring early in the summer season. The timing of these events is particularly noteworthy, as significant mortality impacts were observed during heat episodes occurring in late spring and early summer, before the prolonged July heat event which ran from the 5 July to 17 July and is not included in this report. Early-season heat can pose particular risks as unusually hot weather may occur before people, communities and services have fully prepared and are ready to respond to hot weather conditions. These findings therefore reinforce the importance of heat-health preparedness measures being in place from the start of the season, rather than focusing solely on the warmest periods of mid-summer.

Although these estimates remain provisional and are subject to revision as more complete mortality data becomes available, the magnitude of the impact is already comparable with some of the highest annual heat-associated mortality estimates previously reported through UKHSA’s heat mortality monitoring programme. For context, UKHSA estimated 2,295 heat-associated deaths during the whole of summer 2023, 1,311 during summer 2024 and 1,504 during summer 2025. The highest annual estimate recorded to date remains summer 2022, when 2,985 heat-associated deaths were observed across 5 heat episodes.

These findings are particularly notable because they relate only to the heat episodes that occurred during May and June. A further prolonged heat episode occurred during July 2026 and is not included in the estimates presented here. As a result, the final seasonal total for summer 2026 is likely to be substantially higher than the figures reported in this interim analysis, and will be reported in the annual Heat mortality monitoring report in early 2027.

Understanding different estimates of heat-related mortality

There are several established ways of estimating the health impacts of adverse high temperatures, and different methods can produce different figures because they are designed to answer different questions.

The UKHSA heat mortality monitoring approach uses observed deaths data to estimate mortality associated with specific heat episodes by comparing mortality during periods of heat with mortality during nearby non-heat periods. This makes it particularly useful for understanding the impacts that were actually observed during a specific heat event.

A recently published rapid assessment by academics using established temperature-mortality models estimated approximately 550 heat-related deaths during the May heatwave and approximately 2,200 during the June heatwave in England and Wales, giving a combined estimate of more than 2,700 heat-related deaths across both events. These assessments provided an early indication of the likely health impacts of extreme heat and can also be used to assess the contribution of climate change to those impacts. However, they are not estimates of observed mortality during the event itself and are designed to answer a different question from the UKHSA heat mortality monitoring approach.

Although these estimates and the UKHSA estimates are not directly comparable because they use different methodologies, geographical coverage and assumptions, both analyses indicate that the May and June heatwaves were associated with a substantial mortality impact. The broad agreement in the overall scale of the estimates provides additional evidence that these events represented a significant public health burden and highlights the increasing risk posed by extreme heat in England.

The Office for National Statistics (ONS) climate-related mortality estimates are different again. They use long-term statistical models based on historical temperature-mortality relationships to estimate the overall burden of heat- and cold-related mortality across England and Wales over many years. These estimates are intended to describe the longer-term impact of temperature on population health rather than the effects of a specific heat event.

Public Health Wales publishes annual heat mortality surveillance reports using a comparable heat episode definition and a similar observational approach to UKHSA, although there are some differences in the baseline period used for comparison. Public Health Scotland also publishes annual heat impact assessments using the same approach to calculate observed heat-associated mortality during heat episodes. In addition, Public Health Scotland uses longer-term temperature-mortality modelling to estimate the annual burden of heat-attributable mortality in Scotland.

UKHSA also publishes annual cold mortality monitoring reports. Estimates of heat- and cold-associated mortality reported through UKHSA’s monitoring programmes are also not directly comparable. Although both systems aim to assess the health impacts associated with periods of extreme temperature, they use different methodologies and are designed to capture different aspects of risk. Heat mortality estimates are based on observed increases in mortality during defined heat episodes. Cold mortality estimates are derived from statistical models of the relationship between temperature and mortality that account for the delayed effects of cold weather. As a result, estimates for heat and cold should not be interpreted as directly equivalent measures, nor should changes in one be viewed as offsetting changes in the other. However, mortality estimates associated with recent heat episodes are approaching the scale of those reported for some recent cold episodes, highlighting the growing public health significance of extreme heat.

In simple terms, the Imperial College London approach provides an early estimate of the likely health impacts of a period of adverse high temperatures. The ONS approach estimates the long-term population burden associated with heat and cold. The UKHSA approach estimates what was subsequently observed during a specific heat episode using registered mortality data. As a result, estimates produced using different methods are not directly comparable and should be viewed as complementary sources of evidence that together provide a more complete picture of the health impacts of hot weather.

Data sources and methodology  

This interim report uses the same data, mortality surveillance methodology, analytical pipeline and quality assurance processes as the UKHSA annual heat mortality monitoring report, which is published as official statistics. Although this interim report is not itself an official statistics publication, the principles, methods and standards described in the UKHSA quality and methodology information (QMI) report remain applicable and provide further detail on the approach used.

Heat episodes are identified whenever the mean Central England Temperature (CET) reaches at least 20°C. One day either side of the heat episode is also included in the analysis. It is important to note that decisions about issuing HHAs are based not only on forecast temperatures, but also other meteorological factors like humidity, overnight temperature and any concurrent hazards, but also wider contextual factors that may influence impacts that are eventually observed. Therefore, the alerting periods may not always match analysis periods.

The number of observed heat-associated deaths is calculated by comparing average daily deaths during a heat episode with average daily deaths during baseline periods before and after the heat episode. Consistent with the official statistics methodology, the baseline normally comprises 14 non-heat episode days before and 14 non-heat episode days after the heat episode. However, for the June 2026 heat episode included in this interim report, only the 14 days before the episode were available for the baseline calculation because insufficient non-heat episode days had occurred after the event at the time the analysis was undertaken.

As this report has been produced shortly after the heat episodes occurred, some deaths that have already occurred will not yet have been registered. To account for this, a delay correction has been applied to daily deaths using the average completeness of death registrations observed prior to 2026. This adjustment will not be required in the final annual official statistics publication, which uses a more complete death registration data set available several months after the end of the summer season.

Because daily mortality varies naturally for reasons unrelated to temperature, there is uncertainty around estimates of heat-associated mortality. This uncertainty is represented using 95% confidence intervals, shown in brackets after each estimate. Estimates are considered statistically significant where the confidence interval does not include zero.

Glossary

Central England Temperature (CET)

A temperature data set produced by the Met Office Hadley Centre, which is representative of the temperature in a roughly triangular area of the United Kingdom enclosed by Lancashire, London and Bristol.

Confidence interval (CI)

A confidence interval is a measure of the degree of uncertainty in an estimate based on a sample distribution. Here, 95% confidence intervals indicate that if we repeatedly observed the same process under identical conditions, 95% of the intervals would contain the true value. A wider range indicates more uncertainty in the estimate. Overlapping confidence intervals indicate that there may not be a true difference between estimates.

Heat episode

A period of heat. In this analysis, this is defined as days when the mean Central England Temperature (CET) is at least 20°C.

Heat Health Alert (HHA)

An alert issued by England’s Weather Health Alerting system, warning that hot weather is forecast that could lead to impacts on health for the population of England. Alerts can be issued at yellow (response), amber (enhanced response) or red (emergency response) levels.

Background information

Related statistics

UKHSA publishes several official statistics covering mortality surveillance.

The annual heat mortality monitoring reports are the final estimates of the number of deaths associated with heat in each summer. These reports include further information on cause of death, place of death, and breakdowns by age, sex and region.

The weekly all-cause mortality surveillance reports show time periods when mortality levels were higher than expected, rather than providing an estimate of the number of actual or expected deaths. These reports do not include information on cause of death.

The annual surveillance of influenza and other seasonal respiratory viruses in the UK reports include estimates of the number of deaths attributable to influenza, COVID-19 and extreme cold using all-cause mortality data.

Other assessments of mortality include the number of weekly deaths registered in England and Wales, which is published weekly by the Office for National Statistics (ONS). In 2023 the ONS also published experimental statistics on climate-related mortality in England and Wales, 1988 to 2022.  The different methods used in the UK for mortality assessment, and their varied purposes, are discussed in more detail in Measuring excess mortality: a guide to the main reports.

Further information and contact details

Feedback and contact information

For any feedback or enquiries, please contact: extremeevents@ukhsa.gov.uk

Code of Practice for Statistics 

UKHSA has produced this report in line with the principles and practices set out in the Code of Practice for Statistics on a voluntary basis. We have applied the same standards of trustworthiness, quality and value, including appropriate analytical quality assurance processes, to ensure that the findings are robust, reliable and transparent. We have published a separate statement that explains how we applied the principles of trustworthiness, quality and value to this report.

The Office for Statistics Regulation (OSR) sets the standards in the Code of Practice for Statistics that producers of official statistics are expected to follow. UKHSA is committed to applying these standards across its analytical outputs wherever appropriate. You are welcome to contact us directly at extremeevents@ukhsa.gov.uk with any comments on how we meet these standards. Alternatively, you can contact OSR at regulation@statistics.gov.uk or via the OSR website.