The rail operator - which runs services from Reading to Waterloo via Wokingham, Bracknell and Ascot - says it is continuing to alter services because of the continued forecast for heavy snowfall and freezing temperatures.
Jake Kelly, customer service director for the South West Trains-Network Rail Alliance, said: "The snowy weather is causing disruption to road and rail transport in many parts of the country. We have already seen snow fall on large parts of our network, however the special timetable we have in place is running well and means that trains have more time to cope with the poor weather conditions.
"The revised timetable helps us to ensure we can make the best use of our resources to deliver the most robust service for passengers.
"Services are expected to be busier than normal. We'd therefore advise passengers to check the timetable before they travel and ensure they allow enough time to travel to and from the station.
"Our staff are working incredibly hard to keep as many trains running as possible as well as keeping depots and stations clear and safe, however we understand the impact this is having on our passengers and would like to thank them for their patience during these difficult conditions."
For details of services, see www.southwesttrains.co.uk