Network Rail engineers are out across the South from Oxford to Oxted pumping water away from the railway and monitoring flood sites.
While much of the national network is operating well, and more than 12,000 trains have run today so far, engineers are increasingly finding problems arising from groundwater reaching record highs across the south east.
One of the areas affected by water coming up through the soil is at Maidenhead on the main lines from London Paddington station, where signalling systems have been flooded and had to be disconnected. There are currently four trains an hour out of Paddington, rising to five trains per hour in the evening peak, which represents a quarter of the normal service.
The line from Oxford to Didcot is also flooded, with a limited shuttle service running at reduced speed.
The railway at Datchet, which links Windsor with Staines, remains closed by flooding from the River Thames and is expected to remain so for at least the rest of the week.
Landslip sites that are continuing to cause line closures include those at Botley, between Fareham and Eastleigh, Oxted, and multiple sites between Wadhurst and Battle.
In the West Country, the route from Taunton to Bristol is severed at Bridgwater by the Somerset Levels flooding and the line at Dawlish, linking Exeter with Newton Abbot and the West, will remain closed following sea wall damage for at least six weeks.