The fire service in Surrey has declared a major incident as crews battle an open fire – as crews in the capital fight two other large blazes, with people in west London told to keep their doors and windows shut.
In Surrey, a fire at Hankley Common near Farnham has drawn “several fire engines” to the area.
The fire service tweeted: “There is a great deal of smoke so please avoid the area, windows and doors should be closed if nearby and pets kept indoors.”
Read more: Dramatic satellite pictures show the impact of the heatwave as high temperatures hit country
Pictures online show plumes of smoke rising over the county, with people as far away as Guildford reporting they can see it.
The fire service later tweeted to ask those nearby to stop calling 999 to report smoke clouds, after receiving “an incredibly high” number of calls.
It added some local roads have been closed as a result of the incident.
It comes after a swathe of wildfires in London and the surrounding area after last week’s record temperatures left the ground tinder-box dry.
Fire crews in London are also battling wildfires – with blazes in Rammey Marsh in Enfield, and Cranford Park in Hayes.
In Enfield, close to Epping Forest, London Fire Brigade (LFB) said around 100 firefighters were battling the grass fire, which had grown to the size of four football pitches.
The service urged people to help prevent further fires by not having barbeques and disposing of cigarettes correctly.
A fire in Hayes can be seen from across west London, with the LFB adding 70 firefighters are at the scene. It says people in the area should close doors and windows.
Big Jet TV, which live commentates on planes landing at Heathrow, says that visibility is reducing at the airport, sharing a picture of a smoke covered runway from the nearby fire at Hayes.
The UK hit record temperatures on Tuesday, with Coningsby in Lincolnshire reaching a sweltering 40.3C (104.5F) – the first time since records began that the mercury has exceeded 40C in the country.
Some parts of the UK saw significant damage as a result of the extreme heat, such as house and wildfires, melting airport runways and expanding railway tracks.