England and Wales have seen some of the hottest summers in recent years. The mean temperature for the meteorological summer (June to August) was 17.0 degrees Celsius in 2018 and 16.1 degrees in 2019. Back in 1919, the mean summer temperature was only 14.3 degrees.

With the unusually hot weather come media headlines, warning people against the dangers of the heatwave and how the hot temperatures are leading to an increasing number of deaths – “killer heatwave” stories are not uncommon. But are those headlines backed up by the data? The chart shows provisional data on the impact heat has had on mortality this summer.

The number of deaths increased around the same time as the hottest day on record

Deaths registered and recorded temperatures, England and Wales, May to August 2019

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The hottest temperature of 38.7 degrees was recorded in Cambridge. There was an increase in the number of deaths around the hottest day.

It should be noted that data for 2019 are highly provisional because of the amount of time it can take for deaths to be registered, so the recorded number of deaths per day is likely to increase as more deaths are registered. Therefore, at the moment, comparisons with previous years cannot be made. However, we are able to look more in-depth at summer 2018 deaths.

When comparing the number of deaths per day in 2018 with the five -year average, we can see that some days have more deaths than we would expect. The comparatively high number of deaths occur mainly on days that are defined as heatwaves by Public Health England (PHE) in their deaths relating to heatwaves report.

The total number of deaths across the summer was similar to previous years

Deaths registered and temperatures recorded, England and Wales, May to August 2013 to 2018

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Looking at the chart , we can see that after a rise in deaths, there is a period where the deaths tend to be lower than the five -year average. This means that at a daily level, extreme heat seems to have an impact on the number of deaths, but across the summer period as a whole the number of deaths is similar to previous years. This could be because the most vulnerable people, for example, those with pre-existing respiratory or cerebrovascular diseases are more susceptible to death during heatwaves.

Winter versus summer

Although we see that the hot summer weather has had some effect on deaths, the effect of winter is greater, as shown in our excess winter mortality reports. Looking at 2018, the number of deaths in the winter months are consistently higher than the summer months, even with the heatwaves experienced.

The number of deaths during winter is consistently higher than in summer

Registered deaths, England and Wales, January to December, 2018

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More analysis is due to be published next year

Due to the provisional nature of the data, additional analysis looking at age groups mostly affected or causes of death cannot be currently undertaken. These estimates will be available in the autumn when the data for 2018 are more complete.

This analysis helps us to achieve some of the elements in the UK government’s official statement made in the most recent Global Platform on Disaster Risk Reduction, specifically “In line with the commitment to ‘leave no one behind’, we are accelerating efforts to ensure data are timely, comprehensive and disaggregated.”