Up to 8mm of rain is forecast across parts of the Advertiser and Review region on Christmas Eve.
Flood alerts were in place on the Upper Ouse and the River Tove, and the Environment Agency warned river levels could rise in Brackley, Towcester and Buckingham today, Monday, following the downpour.
In Bicester, the Langford and Wendlebury Brooks and their tributaries from Stratton Audley down to the M40 near Merton were on flood alert today.
The Environment Agency said the river is expected to spill out into the floodplain in the Wendlebury area during this afternoon.
More rainfall is expected on Christmas Day, Tuesday.