Six fire engines and around 40 firefighters were called to marsh and scrubland alight on Ray Lamb Way in Erith.
A hectare of land was destroyed by the fire. There were no reports of any injuries.
Station Commander James Cartwright, who was at the scene, said: "The warmer weather we have been having makes the ground extremely dry, which unfortunately means grassland and parks will burn quickly when exposed to even the smallest of sparks.
“If you see a grass fire, don't attempt to put it out yourself as grass fires can travel very quickly and change direction without warning.
"Call the Brigade and let us know where the fire is.”
The Brigade was called at 2106 and the fire was under control by 2333. Fire crews from Bexley, West Norwood, Erith, Sidcup and Eltham fire stations were at the scene.
Brigade’s top tips on grass fires: