Hot weather, dry conditions and record temperatures in the UK mean increased risks of extreme wildfires, say experts

The UK Fire Danger Rating System project team is warning of further risks of wildfire, which pose extreme danger to wildlife and ecosystems, as the hot and dry weather continues this summer.

The fire weather index has reached a record level this summer

Their analysis has highlighted that the fire weather index has reached a record level this summer. The fire weather index is a numerical indicator which predicts the likelihood of extreme fire behaviour via calculations from long-term and short-term relevant weather measurements; this includes temperature, relative humidity, rainfall and wind.

July 19th was the hottest day since 1979

Dr Tadas Nikonovas explained: “The fire weather index on July 19th was the highest the UK has seen since at least 1979 when the available record began.

“Our visualisation below shows the last 20 years of maximum fire weather index values for England, and illustrates how extreme the conditions were on the day.”

Professor Stefan Doerr, who leads the Centre for Wildfire Research at Swansea University, added: “Our analysis also shows that while we saw heathland fires before and after the record temperatures in July, the catastrophic fires in England on July 19th were concentrated on grasslands and arable land close to densely populated areas.

“Indeed, there were very few fires in more remote areas, which are typically dominated by heathland fuels, on the day of the record temperatures.”

London School of Economics’ Dr Thomas Smith said: “Anecdotal evidence suggests that few people were ‘out enjoying the countryside’ on the day of the extreme heat, because it was simply too hot, reducing the likelihood of ignitions in heathland area – while we know that the grassland and arable fires that led to the unprecedented loss of houses on July 19th may have been ignited close to homes and gardens where people were sheltering from the hot weather.”

Dangerous wildfire spreading on heathland near houses in Poole, Dorset 2022
© Chris Kemp

Flames move faster in low moisture conditions

The University of Birmingham collected vegetation ‘fuel moisture’ data throughout July, and shocking discovered that some of the moisture readings in grassy fuels were extremely low (0-1%).

In fact, these measurements were so low that Professor Nick Kettridge had to point out that, in some cases, it was so low that it was impossible to measure with the commonly-used measurement approach.

“This level of dryness also explains the extreme nature of the fire behaviour, with large flames and fast-moving fires, even in places without high wind conditions,” he concluded.

Hot weather driven by human-caused climate change

Unfortunately, it’s looking pretty bleak – unless nations work together to tackle climate change.

The reality is that unprecedented fire weather and extreme fuel moisture conditions are only going to become more common in the next few decades. And this is a direct impact of humans.

Major retailers stopping the sale of disposable barbeques is welcome news

However, there is a lot that can be done to mitigate the likelihood and future impact of fires, says the University of Exeter’s Professor Claire Belcher.

Belcher explains: “Major retailers stopping the sale of disposable barbeques in some regions is one welcome contribution to reducing accidental ignitions, but with the dry hot weather currently continuing in parts of the UK, the overall fire risk remains very high.”

“The Met Office provide a Fire Severity Index (FSI) – an assessment of how severe a fire could become if one were to start – but this does not provide an assessment of the risk of wildfires occurring,” said project lead Dr Gareth Clay from The University of Manchester.

“To fill this critical gap, our project team are researching the key components that allows the building of an effective, tailored fire danger rating system that can establish the likelihood and impact of wildfires in the country.”


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