Heat-related deaths have rarely been out of the headlines this summer. Now, the UK Health Security Agency (UKHSA) has published an interim report on the May and June heatwaves, estimating that around 2,900 heat-associated deaths occurred in England. That's a striking figure, but as always, the detail behind the number is just as interesting as the headline itself. Here’s what stood out to me.
What does the report say?
UKHSA covers two heat “episodes” in their report: a shorter spell of unusually hot weather in May and a more prolonged and intense heatwave in June. They estimate that around 750 heat-associated deaths occurred during the 4-day May heatwave and around 2,100 in the 8-day June heatwave.
To put the figures into context, provisional data from the Office for National Statistics shows there were around 39,300 deaths registered in England in May and 43,800 in June. So, while heat-associated deaths represent a relatively small proportion of the total, they are still significant from a public health perspective.
Is this unusual compared to previous years?
UKSA publishes a report each year on heat-associated mortality in England. The most recent annual report estimated that there were around 1,500 heat-associated deaths in summer 2025, while the highest annual total on record was around 3,000 heat-associated deaths in summer 2022. But this was spread across five separate heat episodes – the 2026 total is already approaching that level, despite only covering May and June. The prolonged July heatwave isn't included in this analysis, making it seem likely that the final total for 2026 will be higher still.
What counts as a “heat-associated death”?
UKHSA doesn’t count individuals who died “because of heat”. Instead, they estimate how many more deaths occurred during a heatwave than what they would normally expect. To do this, they compare the daily deaths during the heatwave with the average daily deaths that were observed in the weeks immediately before and after it (if available). Any difference is then attributed to the heatwave.
As a result, a heat-associated death isn’t necessarily one where heat is recorded as the cause of death. Some of these deaths may be linked to dehydration, heat exhaustion or heatstroke, but the effects of extreme heat can be much wider than that. For example, hot weather can worsen existing medical conditions, like cardiovascular and respiratory conditions. Research has also shown that extreme heat can disrupt healthcare services, including cancer care, while some medications can make it harder for the body to regulate temperature. Even seasonal factors such as increased outdoor activity may play a role.
Who has been most affected?
At this stage, we don’t know the demographic profile of the extra deaths in 2026. Because this is an interim report, it doesn’t include breakdowns by age, sex, region or cause of death. UKHSA says this analysis will be included in its full annual report which is expected in early 2027.
If the pattern is similar to previous years, most heat-associated deaths are likely to have occurred among older people. In the 2025 report, the highest heat-associated mortality rates were seen among those aged 85 and over, followed by those aged 75 to 84, while there was no statistically significant heat-associated mortality in younger age groups. Heat-associated deaths were also concentrated in the warmer southern, central and eastern regions of England.
Extra or accelerated deaths?
One question we can't answer yet is how much of this reflects mortality displacement. That's the idea that some heatwaves may bring forward deaths that would otherwise have occurred a few days or weeks later, particularly among people who are already in poor health or especially vulnerable to extreme temperatures. If some deaths were brought forward, we would expect a period of higher-than-average mortality would be followed by a period of lower-than-average mortality.
Previous research has found evidence of mortality displacement following periods of extreme heat, particularly among older age groups. It has also been cited as a possible explanation for some of the elevated heat-associated mortality seen during the record-breaking summer of 2022. However, the extent to which mortality displacement occurs can vary considerably between heatwaves, making it difficult to draw conclusions from the interim 2026 figures alone.
So what should we take from this?
For now, the report provides an important early indication of the health impact of this summer's heatwaves, rather than a definitive assessment. We'll be looking out for UKHSA's full report in 2027, which should provide a much clearer picture of who was affected, what drove the increase in deaths and what it means in the broader context of longevity.
This is based on information provided by the UKHSA in their report titled ‘Interim heat mortality monitoring report, England: May and June 2026’ published on 30 July 2026. The UKHSA note: “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.”