What is a 'firewave'? And when will the risks from blazes during this heatwave end?

At least 19 wildfires are burning across the UK as a third heatwave in as many months continues - causing a phenomonon experts have previously called a "firewave".

With the UK seeing temperatures above 34C (93.2F) in May, June, and July for the first time, there has been an increased risk of blazes in rural and urban areas

The high temperatures and heatwave aren't due to end any time soon, with some areas of the country not set to see any significant rainfall for at least another week.

That means a lot of places won't have seen any since a wet spell in mid-June. It's made for perfect conditions for wildfires.

So, what is a firewave? Where are the areas most at risk? And when will we be out of the worst of it?

What is a firewave?

It's not an official term you'll see from forecasters, but experts define a firewave as a phenomenon that happens when multiple wildfires occur in urban areas.

It happens when we have weather much like we have had since June: Extreme heat and high temperatures coupled with drying vegetation and low to no rainfall.

Joe McNorton, scientist at the European Centre for Medium-Range Weather Forecasts, told Sky News: "Across the UK we are seeing a combination of hot, dry weather and vegetation that has become increasingly combustible after a prolonged period without significant rainfall."

He said that the conditions "even in the UK, where large wildfires are relatively uncommon... can allow fires to spread quickly through grass, heath and moorland once they start".

"Importantly, wildfire risk has a memory, and it can take weeks or even months of warm, dry conditions to remove moisture from vegetation and create a landscape that is ready to burn," he added.

Joanna Robinson, Sky weather producer, noted that the prolonged hot spell this summer "has dried out vegetation, while strengthening winds and low humidity are further increasing the fire risk across England and Wales.

"Any fires that do break out, the stronger winds will help them spread faster, making them harder to contain," she added.

Where did the term come from?

The term firewave first originated from Imperial College London research into the wildfires that broke out during the 40C (104F) weather in July 2022 - when more than 100 blazes broke out in London.

The study found that vapour pressure deficit (VPD) - a measure of how quickly vegetation dries out - was the single strongest predictor of wildfire risk.

By way of example, while there were four London heatwaves in 2018 to 2022's three, only one in 2018 had a high VPD, which explained up to 61% of the variation in fire numbers in those two years.

ICL said in its findings that climate change, as well as land use and population, are "driving an increase in wildfire frequency and size" in urban areas.

How many wildfires have there been?

From 6 July to Monday, data from the National Fire Chiefs Council (NFCC) showed that fire and rescue services in England and Wales responded to 342 wildfires.

And according to the NFCC, there were 19 wildfires active in England and Wales as of Monday.

In response to multiple fires, including those in Rhinog National Nature Reserve and the Conwy Mountain area, North Wales Fire and Rescue Service has declared a major incident.

Meanwhile, Staffordshire Fire and Rescue Service and West Midlands Fire Service have activated a mutual aid arrangement due to the volume of emergency calls being received.

Blazes have also been reported in Orpington in London, and in the Peak District.

Where are the risks from wildfires?

As conditions have stayed hot and dry for almost an entire month, much of England and Wales is at risk.

A chart from Natural England has most of the two home countries classed as very high under the Fire Severity Index.

Areas with a lower risk are in the northeast of England, under high or moderate risk, and the northwest, mostly under high risk.

Elsewhere it's a little less extreme: As of Tuesday, neither Scotland nor Northern Ireland's fire services have issued a wildfire warning, but both are urging caution during high temperatures.

Europe is battling similar fire risks though, with a wildfire tearing through the historic Fontainebleau forest near Paris on Monday. Two have since been arrested on suspicion of starting the fire.

And Spain has been battling one of its deadliest wildfires on record. Authorities there identified a British woman as a victim of the fire on Monday, the fifth known to have died from the UK.

When will firewave conditions end?

Not for another week at least: Joanna Robinson, Sky weather producer, said that parts of England and Wales are expected to remain in heatwave conditions until at least the weekend.

See the weather forecast for your area

This is due to "a marked diffluent block," which she explained occurs "when an area of high pressure sits directly above an area of low pressure, splitting the jet stream and causing little movement in the weather pattern, which can last for weeks".

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Ms Robinson added: "High pressure is currently sitting to the north of the UK, which is bringing dry conditions to the country, with just a small chance of showers or thunderstorms in the southwest on Wednesday and Thursday.

"Temperatures will remain well above average in the south over the next few days, with the heat also returning to parts of the north.

"By the weekend, temperatures will be a bit lower but will still be above average and reaching the mid to high twenties."

(c) Sky News 2026: What is a 'firewave'? And when will the risks from blazes during this heatwave end?