Rail operators are warning of major disruption to services across the network today.
South West Trains have cancelled 27 trains and made 113 timetable alterations.
This will affect those travelling on the West of England mainline calling at Crewkerne, Yeovil Junction, Sherborne, Templecombe and Gillingham.
A spokesman for South West Trains said: "Starting from 1300 on Monday 23 December and until at least 0600 on Tuesday 24 December, all trains will have to run at significantly reduced speeds across the whole South West Trains network.
"After 13:00 we will make the following service alterations to minimise delays and congestion while we run at reduced speed.
"Waterloo to Exeter/Yeovil Junction services will terminate at Salisbury.
Exeter/Yeovil Junction to Waterloo services will start from Salisbury."