“The forecast is for continuing freezing weather and for more snow on Monday evening which will have an effect on services,” said a spokesman for Southeastern trains.
Late evening delays are more likely than delays in the morning, he said.
If track temperatures stay below zero degrees then any moisture will freeze, threatening services in and out of London.
The Met Office has issued a severe weather warning for the South East of heavy snow and widespread icy roads.
“We strongly advise customers to check our website for the latest information,” said First Capital Connect.
South West are running “ghost trains” through the night to stop lines freezing.
Employees will be redeployed to stations near their homes, in order to keep the network staffed, said Corinne O’Loughlin of South West trains.
Tube and bus services are in “pretty good stead,” according to a spokesman for Transport for London.
Overground trains are carrying de-icing spray to apply to the rails, he said. Some battery locomotives are sent over lines throughout the night to prevent freezing.
Out of 700 bus routes, only 90 are being diverted, he said.
Yet Tube services were affected on Saturday, disrupting weekend shoppers. Strike actions added to frustrations, bringing down a section of the Bakerloo line.
Flights in and out of the capital are facing severe delays, causing misery for thousands.
No planes were allowed to land at Heathrow airport yesterday, with further cancelations expected today.
Delays will spill into the rest of the week, the airport said.
“As airlines move diverted aircraft and crew back to their normal positions, there will be further cancellations and delays in the days that follow,” a Heathrow spokesman said.
Passengers are advised to check all flights with their airlines, and can check Heathrow updates on the airport’s Twitter page.
Meanwhile, the snow has provoked a political storm in Westminster, with shadow chancellor Alan Johnson accusing the coalition government of harming the economy by being unprepared for the weather.
“It is a big issue,” Johnson said, “when people believe the government has left them to it: ‘get a shovel or stay at home.’”
But William Hague dismissed the claims as “the heavy snowfall of political opportunism”.
TRANSPORT | MONDAY SERVICES ON TRAINS AND PLANES
● Southeastern trains
We expect services will be disrupted throughout the day. Passengers with Mainline tickets can use the High Speed services at no extra cost.
● South West trains
A revised timetable is running. We are going to try to run a very robust service, as much as possible.
● Southern railways
Running a normal service. Services may be subject to short notice alterations and cancellations. We are in some cases running longer trains.
● National Express East Anglia
Running an amended timetable on Monday to mitigate the impact of the very low air temperature.
● First Capital Connect
We are planning to operate our normal timetable on Monday. Expect cancellations between Peterborough and London.
● Heathrow airport
There will be further cancellations and delays.
● Gatwick airport
Knock-on delays and cancellations are likely.