Do summer heatwaves lead to an increase in deaths?

The Office of National Statistics (ONS) have investigated whether there is a link between heatwaves and numbers of deaths.

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.

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

When comparing the number of deaths per day in 2018 with the five -year average, 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).

However, the data shows that at a daily level, while extreme heat seems to have an impact on the number of deaths, the number of deaths across the summer period is similar from year to year. 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.

Although 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.

Read the full report on the ONS website here.