What is a 'firewave'? Experts issue weather warning for UK cities this weekend

Yahoo

a day ago

Experts have warned people in densely populated areas to be alert this weekend
People in major UK cities including London have been urged to "stay alert" this weekend amid the threat of so-called "firewaves", as the fourth heatwave of the summer creates the perfect conditions for blazes to get out of control.
Firewaves is a term used by researchers at Imperial College London (ICL) to describe a period of time when many wildfires break out in a city at the same time.
Professor Guillermo Rein, lead researcher at ICL, said prolonged dry spells can lead to grass, plants and vegetation losing a lot of moisture, making even small sparks able to cause huge fires that spread quickly.
Asked about the threat facing London this weekend amid the ongoing heatwave, Prof Rein told Yahoo News: "Stay alert, but keep calm and carry on. Be careful with anything that could start a fire in vegetation. Awareness and prevention are key."
He warned that multiple, urban wildfires igniting at the same time could "overwhelm the fire services and force evacuations in just a few hours".
The team at ICL pointed to 19 July 2022, which saw a series of unprecedented wildfires in London, which overwhelmed the London Fire Brigade (LFB) as it experienced its busiest day since the Second World War.
The warning comes amid forecasts of extreme heat this weekend, with London especially at risk due to its vast green spaces next to residential areas.
The LFB has dealt with three separate heath fires in the capital recently, while a wildfire warning was issued for most of Scotland for the 10th time this year following a large blaze on Arthur's Seat on Sunday.
It told Yahoo News it considered the risk of wildfires in London at the moment as "severe".
What is a 'firewave'?
Firewaves refer to clusters of multiple wildfires erupting at once in urban environments, triggered by extended periods of hot, dry weather.
They can start after several days without rain, when dry vegetation essentially becomes a highly flammable fuel.
Human activities, such as accidental sparks or arson, often ignite them, but the underlying driver is atmospheric conditions that suck moisture from the land, known as vapour pressure deficit (VPD).
When VPD is high, plants begin to struggle to get moisture to their leaves and begin to wilt, rapidly increasing how flammable they are.
In ICL's research, they looked at how much water the LFB pumped during wildfire events in London and classed the most severe outliers as firewaves.
They found that between 2009 and 2022, four firewaves occurred in London, one in 2018 and four in 2022.
Over the summer of 2022, 40 hectares of grassland were destroyed, 37 buildings were damaged, five cars were destroyed and 88 homes were evacuated.
Dr Douglas Kelley, land surface modeller at the UK Centre for Ecology & Hydrology, told Yahoo News: "Research by Imperial College London shows that just 10 days without rain can leave grass and plants, especially dead or brown vegetation left over from this year's droughts, ready to burn."
What cities are at risk?
Any big city with parks, green spaces and abundant vegetation could be hit, according to Prof Rein.
Dr Kelley said that such places - people and nature meet - are known as the "urban–wildland interface". "We've seen these fires across England in recent years, and the blaze on Arthur's Seat in Edinburgh this week shows the risk is UK-wide," he said. "Cities around the world face similar dangers: this year's fires near Los Angeles and in Chile show how serious it can be."
In the UK, London is particularly vulnerable to firewaves, given the large number of parks and green belts bordering densely populated areas, creating ideal pathways for fire to spread.
Dr Kelley explained: 'When it's hot and dry, everyone needs to be extra careful outdoors. Most wildfires in the UK are started by people, often accidentally.
'Disposable barbecues in parks can ignite grass. Litter – especially glass bottles – can focus sunlight and spark fires. Cigarettes are a common cause. Staying alert and avoiding risky activities can make a big difference to you and other people nearby
Other major cities like Manchester, Birmingham, and Edinburgh face similar threats, especially where urban expansion meets flammable vegetation.
Health risks aside from the dangers of fire itself include smoke inhalation, while ecological damage can harm local plant and animal life.
Prof Rein added: 'The potential for fires to spread into homes is very real.'
Will firewaves and wildfires become more likely?
Firewaves will become more likely in the UK as climate change intensifies heatwaves and dry spells, Dr Kelley warned.
He said that UK Centre for Ecology and Hydrology research, alongside the Met Office, shows fires in 2022 'were made at least six times more likely by human-caused climate change'.
He added: 'As temperatures rise, wildfires will pose a growing risk to people, property and nature, even in the UK.
Scientists predict a surge in such events, with risks 'much greater now than a decade ago,' according to Professor Rein.
Kelley said that countries like Australia, which have a long experience with wildfires, can help authorities in the UK prepare for similar outbreaks here.
He said public campaigns can make people know when fire bans are in place, while the UK could learn more from other countries. "In Europe, the US, Canada and Australia, fire services also share resources across regions during major outbreaks," he said. "Similar planning and cooperation here, alongside preparation, prevention, public awareness and land management, will help reduce the risks."