Four fire engines and around 25 firefighters were called to grass alight in Richmond Park in Richmond.
Around one hectare of woodland and shrubland was alight.
A London Fire Brigade spokesperson said: "Although the temperature has cooled down, we are still asking people to take care to prevent grass fires.
"We’re asking the public to take care not to drop cigarettes or matches on dry grass and to keep a very close eye on barbecues.
"Dropped glass can also start fires as the sun can magnify the sun’s rays.
"Grass fires can quickly spread and cause serious damage, so if you see grass smouldering, please call 999 immediately.”
• Never leave camp fires or barbecues unattended and extinguish them properly after you have finished using them
• Clear away bottles, glasses and any broken glass to avoid them magnifying the sun and starting a fire
• Dispose of smoking materials such as cigarettes safely
• Explain to children the dangers of playing with and lighting fires
The Brigade was called at 1433 and the fire was under control at 1608. Fire crews from Kingston, Surbiton and Richmond fire stations attended the scene.