Rail passengers have been warned to check travel information on Thursday (February 23) as Storm Doris is set to bring gale force winds.
Trains will be running at reduced speeds to keep passengers safe during the high winds in case trees or other objects are blown onto the tracks.
Gusts of up to 70mph could hit parts of London as the Met Office raised the severe weather warning in parts of the south to amber.
Chief operating officer of Network Rail South East, Andy Derbyshire, said: “Gale force winds are forecast on Thursday, so we're putting a 50mph speed limit in place when winds are strongest to limit the risk to passengers and staff should trees or other objects get blown onto the tracks."
He added: “This is part of our standard planning for stormy weather, but it will mean changes to journeys for some passengers.
“Your safety is our top priority, so thank you for your understanding and please check before you travel.”
Storm Doris is the fourth officially named system of the winter and the weather warning includes parts of London and south east England.
Heavy rain is also expected to be brought in by the storm, with snow in some higher parts of the UK.
A spokesman for Southern Rail said: “These speed restrictions mean that we won't be able to run our full service on some of our routes, leading to cancellations and delays.
“Our advice is to check before you travel for the latest information about your train.”
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