Commuters have faced disruption to their journeys after snow fell across the capital on Friday afternoon.
There were delays at Heathrow, Gatwick and London City airports, and EasyJet has cancelled all flights from Gatwick between 0600 and 1000 GMT on Saturday.
First Capital Connect is running revised timetables on some routes, and Southern, Southeastern and South West Trains have altered Saturday schedules.
Mayor Boris Johnson said the capital's roads were prepared for more snow.
"Even if it snows, 24 hours a day, morning, noon and night for two weeks, we will have enough grit for our roads," Mr Johnson said.
"What I can't guarantee is that some parts of London, if there is heavy snowfall, coupled with ice, bus routes have to be diverted."
Forecasters are predicting up to 5cm (2in) of snow in the capital over the weekend.
BBC London weather forecaster Peter Cockroft said Friday night would be cold but generally dry with the risk of a few snow showers and a minimum temperature of -4C (25F).
The snow would move across London from the west on Saturday, he added, with a maximum temperature of 0C (32F).
And Sunday would see more snow and remain very cold, he said.
Bookmakers have slashed the odds of a white Christmas, with William Hill offering 6/4 for it to snow in the capital on 25 December.