UK should expect summers above 40°C in next decade, warns Met Office

The UK should urgently prepare for summer temperatures in excess of 40°C (104°F), according to the Met Office, the country’s national weather service, which warns the likelihood of extremely high summer temperatures is increasing rapidly as the climate warms.

Temperatures in Lincolnshire, in the east of the UK, hit a record 40.3°C (104.5°F) in July 2022, the highest level ever recorded in the country. The heatwave was made at least 10 times more likely by climate change, scientists said at the time.

Now researchers are warning such extremes won’t be an isolated event. The team, led by Gillian Kay at the Met Office, used a climate model to simulate more than 2500 UK summers to assess the kinds of extremes possible under 2023 climate conditions.

The results show there is a 50 per cent likelihood of temperatures above 40°C occurring in the next 12 years, with the south and east of England most vulnerable to heat extremes. The chance of such extreme heat has risen rapidly in recent decades, increasing sixfold from the 1980s and almost tripling since 2000, the research shows.

Meanwhile, temperatures over 42°C (107.6°F) have a 1 per cent likelihood of occurring in any given year, and the maximum possible temperature the UK could see under current climate conditions is 46.6°C (115.9°F) – although this peak would be “exceedingly rare”, says Kay.

The simulations also give meteorologists a sense of the weather conditions needed to produce extreme heat in the UK. The most likely scenario is a persistent heatwave settling over Europe, with the hot air then moving across the UK’s south and east coasts. This week the Met Office warned a fresh heatwave loomed for the UK, triggered by intense warmth across the European continent.

Heatwaves have become more persistent as the climate has warmed. The hot summer of 1976 saw daytime temperatures remain above 28°C (82.4°F) for a fortnight – under today’s climate, such conditions could persist for well over a month, the new research shows. Simulations show three or four consecutive days of temperatures above 40°C are also possible under current conditions.

“Temperatures several degrees above the 40°C that we saw in July 2022 are possible, and we should be preparing for those,” says Kay, pointing out that as the climate warms, such temperatures become increasingly likely. During the July 2022 heatwave, the UK struggled to cope with even a brief burst of heat above 40°C. More than 1200 excess deaths were recorded, rail transport was disrupted, schools were closed and wildfires swept through the countryside.

Kay urged public authorities – particularly those responsible for public health – to “stress-test” their systems to ensure they can adequately cope with such extreme temperatures. “The Met Office and other similar organisations have said for a long time now that with climate change, we should be expecting more intense and more frequent heatwaves,” she says. “This is exactly what we’re seeing in the study.”

Prolonged heatwaves are dangerous. Not only do they strain environmental ecosystems – drying out soils, wilting plants, stressing animal life – but they also pile stress on the human body, especially if both daytime and nighttime temperatures remain high for a long period. Longer-lasting heatwaves significantly increase the risk of death from cardiac arrest and stroke. The risk is highest in regions where persistent hot weather is unusual, such as in the UK, as homes rarely have air conditioning.