A Flood Alert has been issued by the Environment Agency for the River Thame and Chalgrove Brook.
Flooding is possible for the River Thame from Marsworth to Dorchester including, Long Marston, Rowsham, North Ayelsbury, Cuddington, Thame, Shabbington, Ickford, Waterperry, Cuddesdon, Wheatley, Quarrendon, Drayton St Leonard, Overy, the Chalgrove Brook at Chalgrove and Stadhampton.
Low lying land and roads will be affected first.
The Environment Agency's advice is "be prepared"
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Tuesday's weather for the west of the region
Tuesday's weather for the east of the region
A further 85 buses are expected to arrive on Tuesday and Wednesday, with officials saying the entire operation will last at least a week.