Weather forecasters have warned that Notting Hill Carnival could be hit today by lightning, thundery downpours and half a month's worth of average rainfall.
Hundreds of thousands of revellers descended on west London on Sunday for Family Day - but despite dire predictions the weather remained largely dry.
Conditions are likely to be wetter for the main Bank Holiday Monday parade today after the Met Office issued issued a yellow weather warning for London, the South East, and eastern England.
A spokesman said: "Thundery showers or areas of heavy rain are likely to affect some southern and eastern parts of England. Lightning may be an additional hazard.
"The public should be aware of the risk of localised impacts from heavy rain and flooding, which may affect travel and some outdoor events."
Up to 25mm, or half an average month's rain, could fall in some areas.
Police were kept busy throughout Sunday and made 92 arrests by 8pm, with three for criminal damage, 12 for public order offences, seven for possession of an offensive weapon, 10 for going equipped for theft, 25 for drugs, seven sexual offences, one for GBH, seven for ABH and 20 others.
By 9pm on the street festival's first day last year there had been 95 arrests.
Officers monitored the event with a significant presence on the ground and also from the sky with a helicopter.
Scotland Yard said that a 15-year old boy had been charged with being in possession of a knife at the Carnival Panorama event in Pleasance Park, North Kensington, on Saturday.
The boy will appear on bail at Hammersmith Youth Court on September 14.
As part of his bail conditions, he will not be able to attend the Notting Hill Carnival, and he will be subject to a curfew.
Youths could be seen inhaling nitrous oxide, known as "hippy crack", from balloons and discarded pressured canisters of the substance littered the streets.
The gas, also known as laughing gas and which has several legitimate uses, has been the subject of controversy as a party drug which can cause hallucinations and even death.
Users experience feelings of euphoria, relaxation and calmness, but it can also cause dizziness, difficulty in thinking straight and laughing fits.
It is not illegal to possess but cannot be sold to those under 18 if they are believed to be likely to inhale it, according to the Government's drug education website Frank.
Police said officers on patrol seized 350 canisters of nitrous oxide on a sound system on Ledbury Road, Notting Hill.
No arrests were made and the matter has been referred to Westminster City Council for street trading offences.
Earlier this week dozens of people were arrested in dawn raids against potential troublemakers ahead of the street party.