More than 350 firefighters are tackling at least four grass fires which began burning on Tuesday(July 19).
The London Fire Brigade (LFB) has deployed 100 firefighters after a large fire spread to homes in Wennington, east London.
The LFB says the weather means grassland “will burn quickly”.
A spokesperson said: “Common causes of grass fires include carelessly discarded cigarettes or matches, as well as rubbish left lying around such as glass bottles, which can start flames by magnifying the sun’s rays.
“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.”
About 175 firefighters have been tackling a grass fire on Pea Lane in Upminster, east London, with smoke billowing over the M25 motorway.
Eight fire engines with 60 firefighters have been sent to tackle one of the Croydon fires, in Shirley Hills in south London.
Another four fire engines are also dealing with a grass fire on Chapel View in South Croydon, where about one hectare (2.5 acres) of woodland and undergrowth is alight.
While 10 fire engines are also have been tacking a fire in Palmers Green, north London. 70 firefighters are at the scene where a fire broke out this morning at Aksular restaurant.
In Wembley eight fire engines and around 60 firefighters tackling a blaze at The Broadway, Forty Ave.