The brigade's assistant commissioner Jonathan Smith said the service had already been preparing for an expected increased risk, but added that risk was now “immediate”.
The LFB is urging people to “take extra care and help us prevent fires on open land”.
They are asking people to make sure rubbish, especially glass, is safely thrown away and that cigarettes are properly disposed of.
“Grass will be tinder dry after periods of hot weather, so please don’t have barbecues in parks and public spaces,” a spokesperson said.
It comes after firefighters battled a number of grass fires in the capital over what the LFB called an “exceptionally busy” weekend, when it dealt with more than double the amount of 999 calls it usually receives.
Emergency services took 964 calls on Saturday and more than 1,337 calls on Sunday, which is more than double the 450 calls it usually receives on average per day.
As well as significant blazes in Enfield, Hayes and Thamesmead, fire crews also attended several smaller grass fires in the capital.
Meanwhile, the brigade said a fire in Wanstead on Sunday was caused by a disposable barbecue and a fire in East Ham on Thursday was due to the unsafe disposal of smoking materials.
The National Fire Chiefs Council has warned cities they need to prepare for wildfires after dozens of “unprecedented” blazes broke out during last week’s record breaking temperatures.
In a statement carried by the BBC, National Fire Chiefs Council (NFCC) tactical advisor David Swallow said “services need to recognise the risk they’ve now got”.
“If they don’t, then they’re naive,” he added.
The LFB has said it will “learn lessons” from the recent fires that have ravaged the capital during the heatwave, including in Wennington where 19 homes were destroyed by a blaze in the east London village.
A LFB spokesperson said: “We are constantly looking at developing our equipment and procedures to meet all the new challenges that we face.
“We will learn lessons from the recent intense grass fires, evaluate our response and put in place any additional training that will help to keep Londoners and our firefighters safe.”