Research and analysis

Interim heat mortality monitoring report: Voluntary application of the Code of Practice for Statistics

Published 30 July 2026

Applies to England

The interim heat mortality monitoring report provides an early assessment of heat-associated mortality during 2 notable heat events, one in May 2026 and the other in June 2026. The report supports understanding of the public health impacts of hot weather and informs future preparedness and response activities.

The UK Health Security Agency (UKHSA) already publishes annual heat mortality monitoring reports as official statistics. These reports provide the final estimates of heat-associated mortality for the previous summer. This interim report differs from the existing official statistics because:

• It provides timely provisional estimates of heat-associated mortality, while the official statistics provide the final estimates of heat-associated mortality
• It covers 2 heat periods, while the official statistics cover the whole summer
• The interim report does not provide breakdowns by age, sex, geography, place of death or cause of death, while the official statistics do

The estimates presented in interim heat mortality monitoring report should be viewed as provisional. They are expected to differ from the final estimates in the official statistics because the official statistics allow more time for additional death registrations to be received and processed.

Official statistics

The interim heat mortality monitoring report is not designated as an official statistic because:

• it is a one-off release published in response to a period of exceptionally hot weather
• we could not pre-announce the release of the statistics in advance, due to the short production process

However, UKHSA has produced the interim heat mortality monitoring 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 high standards of trustworthiness, quality and value, including appropriate analytical quality assurance processes, to ensure that the findings are robust, reliable and transparent.

This statement explains how we have applied the principles of trustworthiness, quality and value when producing and publishing the statistics.

Trustworthiness

Trustworthiness means that the public can have confidence in the people and organisations that produce statistics. It reflects the integrity, professionalism and impartiality of the producers and the statistical system. Trustworthiness signals that statistics are not subject to manipulation or undue influence. 

The statistics were produced by a team of scientists and analysts in UKHSA’s Extreme Events and Health Protection (EEHP) team. This is the same team that produces the annual heat mortality monitoring reports. The team was supported by statisticians in the Analytical Quality Assurance and Standards division and the Head of Profession for Statistics. The statistics were therefore produced by subject matter experts, without outside influence.

The statistics are presented impartially and objectively. The statistical commentary is factual, rather than speculative, and conclusions are based on the data and other published evidence. The statistics are used to support UKHSAs public health messaging, but these public health statements are always published separately. The EEHP team also advises ministers and senior officials on the appropriate use of the statistics, including their limitations. This helps ensure that they are not communicated in a misleading way.

As far as possible we have followed UKHSA’s official statistics release practice policy, meaning that:

• Any unplanned corrections and revisions will be handled transparently
• Access to the report before its release was restricted to those involved in its production, and for quality assurance and operational purposes
• Pre-release access to the statistics in their final form was limited to eligible recipients with proper justification, for 24 hours before the publication of the statistics
• Operational access was granted to 3 individuals, 5 days before publication, to develop communications and public health messaging to be published separately to the statistics
• We have published a list of pre-release access recipients

There was one part of the official statistics release policy that we could not follow: We could not pre-announce the release of statistics with the time and date in a 12-month release calendar. This is because the statistics have been published quickly in response to a period of exceptionally hot weather. This was to:

• maximise the value of the statistics to users by publishing as close to the heat event as possible
• support UKHSA’s ongoing public health activities by publishing during the summer, rather than waiting until the publication of the annual report in 2027
• provide reliable information to the public and ministers , which is important given that there was an amber heat-heat alert in place in the week that the interim report was published

Quality

Quality is about using suitable data and appropriate methods to produce reliable statistics that meet user needs. Statistics should inform rather than mislead, and producers must uphold high standards of transparency and quality assurance.

Production

The interim heat mortality monitoring report uses the same data, mortality surveillance methodology, analytical pipeline and quality assurance processes as the annual heat mortality monitoring reports. The quality and methodology information report describes how these reports are produced.

Data on deaths was derived from the Office for National Statistics (ONS) death registrations data. This is a comprehensive record of deaths occurring in England because the registration of deaths is mandatory. ONS checks and quality assures this data to ensure it is suitable for use.

The report was produced using R. The production of the figures and the supplementary data tables was automated, reducing the risk of human error. The code was version-controlled using Git and follows Reproducible Analytical Pipelines principles.

Quality assurance

The code was independently reviewed by an analyst outside the production team, in line with AQuA Book recommendations. The code was run by a second analyst to check that outputs were reproducible. Further quality assurance was done after running the code. Finally, the report was quality assured and signed off by an SCS analyst (e.g. Director of Analysis) or departmental review committee.

Communicating quality

The purpose of the statistics is to provide an early assessment of heat-associated mortality during the heat episodes that occurred during May and June 2026. Therefore, the statistics present provisional data. Users are advised that:

• final data will be published in spring 2027, in the next heat mortality monitoring report
• the provisional data presented in the interim report will differ to the final data

The interim report estimates the number of heat-associated deaths, based on observed mortality. We report the central estimates and their associated confidence intervals to indicate the level of uncertainty associated with the estimates. Confidence intervals are defined in the glossary section of the report, along with some other important concepts.

Throughout the report we are open about how the statistics can be used and their limitations.

Value

Value means that statistics benefit the public by informing and supporting decision making, action and debate. It also means that statistics can be accessed, understood and used by a wide range of users. Providing value is the ultimate goal of statistics, as it reflects their contribution to society and the public good.

Relevance, purpose, and context

UKHSA already publishes annual official statistics on heat-related mortality. The next annual report, covering summer 2026, is due to be published in spring 2027. The interim report presents early provisional data ahead of the annual official statistics. It provides the first estimates of heat-associated mortality during the recent hot weather. We have published the interim report because of the public health significance of these events, and the considerable interest from policymakers, partners and the public.

The interim report explains the statistics in the context of the other reports already published on the subject. In particular, Imperial College London published UK climate heat health risks May and June 2026 in July 2026. This publication also reported on the May and June heat events, but its estimates were based on modelled mortality rather than observed mortality. We explain to users how the reports differ and advise on the comparability of the results.

We also advise users on how and if the interim report can be compared with other mortality statistics published across government.

Accessibility and clarity

The interim heat mortality monitoring report is published as part of the UKHSA ad hoc statistical publications collection and is freely available.

The statistics are published on GOV.UK, which means that they inherit the accessibility features mentioned in the accessibility statement for www.gov.uk.

The statistics include charts and written commentary to help users interpret them.

They also include simple main messages that describe the most important results.

The report also includes a glossary that explains any important concepts needed to understand the statistics.

Feedback

We will continue to gather feedback on the content and value of the statistics. This will inform developments for future heat mortality statistics.

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.