Wildfires and grassfires: what are they and why do they happen?

With the UK at increased risk of wildfires and grassfires due to heatwaves, here’s a guide on what they are, how they start and what you can do before, during and after a wildfire.

Last updated 8 August 2023

Climate change means that heatwaves are getting hotter and longer. In the summer of 2022, the UK experienced three heatwaves and hit temperatures over 40 degrees for the first time. According to a report from the World Weather Attribution, climate change made the 2022 heatwaves 10 times more likely. 

It also says that 2022 was the warmest year since records began in 1884 and that both events are likely down to ‘human-induced climate change’. If this pattern repeats itself, we could see more wildfires and grassfires breaking out across the UK. We have to adapt, and the more we know about the fires, the better we'll be able to prevent them.

What is a wildfire?

A wildfire is an uncontrolled, destructive fire that spreads rapidly through woodland, heaths, grassland and farmland.

Wildfires are unpredictable and can change direction, posing a real threat to people, wildlife, property and the environment. They tend to break out in rural areas but can also break out over open land such as heaths. 

What is a grassfire?

A grassfire is a fire in an area of grassland, such as lawns, parks and commons. We saw several grassfires break out in the UK during the summer of 2022 with record-breaking temperatures, threatening lives and property.

Extended periods of hot and dry weather can increase the risk of a grassfire. This is because grass becomes very dry and straw-like without rain, and even the smallest of sparks can cause it to burn very quickly.

Is a grassfire the same as a wildfire?

A grassfire can happen in any dry, grassy area. A wildfire spreads through forests and areas of wild land such as moors. Both spread quickly and can cause devastation.

How do grassfires or wildfires start?

Long periods of hot, dry weather and a lack of rain make fires more likely. But hot weather alone cannot start a grass or wildfire.

Any burning spark can start a grass or wildfire, and most of these come from human activity.

A smouldering cigarette dropped onto the grass – or thrown out of a car window - is very likely to cause a grass fire in dry conditions. Make sure you extinguish cigarettes properly and throw them away when you get home.

Embers from disposable barbeques can be carried by the wind and cause fires that way. Barbeques can also retain heat after use, so never abandon a disposable barbeque. Always make sure you put it out properly and throw it away.

For these reasons, the London Fire Brigade has strongly advised against using disposable barbeques during heatwaves, on balconies and on open land during heat weather alerts to help prevent grassfires and wildfires. This applies to London and the rest of the UK.

Some supermarkets have temporarily stopped selling disposable barbeques to reduce risk during the heatwave.

Glass bottles are another cause of wildfires. They magnify the sun and can spark fires if left in, or near dry grass. Take them home and recycle them.

“Every one of us can help reduce the risk of fire and keep our communities clean, make sure rubbish is safely thrown away and cigarettes are always properly disposed of." London Fire Brigade Spokesperson 

How do wildfires or grassfires start naturally?

Long periods of hot, dry weather and a lack of rain make fires more likely, but hot weather alone can't start a wildfire or grassfire. Dry grass cannot catch on fire from the sun alone; it requires a spark to ignite it. During a heatwave, a tiny spark can more easily ignite a wildfire or grassfire. As most sparks are caused by human activity, we must be extra careful during periods of extreme heat and dryness.

How fast does a wildfire spread?

Generally, wildfires can travel at a rate of up to 14.27 miles per hour. However, how fast a wildfire or grassfire spreads depends on the conditions, such as the area or terrain, whether it's on a slope, wind speed, fuel and the weather. As Dr Rory Hadden, Senior Lecturer in Fire Investigation, explains, "Periods of hot dry weather result in perfect conditions for fires in vegetation to grow and spread rapidly."

“Periods of hot dry weather result in perfect conditions for fires in vegetation to grow and spread rapidly. In addition increased recreational activity in these areas of vegetation will lead to more fires starting." Dr Rory Hadden, Rushbrook Senior Lecturer in Fire Investigation, University of Edinburgh 

How can we prevent wildfires and grassfires?

The London Fire Brigade gives the following advice:

• Don’t drop cigarettes or anything that is burning on dry ground
• Don’t drop cigarettes out of car windows, as they may land on dry grass by the roadside
• Avoid having barbecues in parks and public spaces
• Never leave campfires or barbecues unattended and extinguish them properly after you have finished using them
• Position your barbecue on level ground and keep it well away from anything that may catch fire
• Do not barbecue on balconies,  as the wind may carry smouldering ash towards nearby grassland. If you’re barbecuing near dry grass, have a bucket of water or sand nearby for emergency use
• Be aware that children, animals, balls or other things may knock over barbecues, increasing the risk of grass fires, especially when in busy parks or public spaces
• Dispose of glass bottles properly. Sunlight can become focused as it shines through the glass, starting fires
• Keep children away from lighters and matches.

 

Why were wildfires so frequent in the UK in 2022?

Summer wildfires increased by 118% during the summer of 2022. According to data obtained by PA Media in a freedom of information request, fire services in England recorded at least 24, 316 between June and August that year, in comparison to 6,213 during the same period in 2021. More than 800 fires alone were recorded on the hottest day of the year, 19 July,

There are several reasons wildfires broke out in the UK during the summer of 2022. An exceptionally dry winter and spring, followed by record-breaking temperatures in July, led to lengthy periods of hot, dry weather.

On top of this, there had been little rainfall, so the ground had become parched and grassy areas had become dry and straw-like. This led to uncontrolled fires breaking out, both in urban and rural areas. In Wennington, East London, a grassfire destroyed nearly 20 homes, 12 stables and five cars. Elsewhere, wildfires broke out in Norfolk, Suffolk, Lincolnshire, Leicestershire and Yorkshire, as well as a ferocious grassfire near Heathrow airport.

Nobody was hurt, but it could have been very serious.

According to research by the Met Office and the UK Centre for Ecology and Hydrology, there is projected to be a global increase of extreme fires of up to 14 per cent by 2030, 30 per cent by 2050 and 50 per cent by the end of the century.

“There is projected to be a global increase of extreme fires of up to 14 per cent by 2030, 30 per cent by 2050 and 50 per cent by the end of the century." The Met Office 

What should I do if I see a grassfire or wildfire?

Wildfires and grassfires spread at lightning speed, and are hard to put out. If you see dry grass smoking or smouldering, stay calm and call 999 immediately. Don’t assume someone has already reported it.

More advice on wildfires and grassfires

Wildfires and grassfires are a risk during long periods of hot and dry weather. Make sure you are prepared to act with our advice on preparing and dealing with wildfires and grassfires. 

• Prepare for wildfires and grass in the UK