The Nene stretch includes the Billing Aquadrome holiday caravan park where hundreds spent Christmas out of their homes after being evacuated.
But emergency services are not expecting anything that serious this time despite Met Office forecasts of more heavy rain in the area.
An Environment Agency spokesman said: "Over the last several days we have seen heavy rainfall in the Middle Nene area, River Ise and tributaries between Clipston and Wellingborough and Alledge Brook between Grafton Underwood and Thrapston.
"This means that the Nene and associated tributaries have risen and remain high, which has led to flooding of low lying land and roads close to the river.
"Further rain is forecast over the next few days and we expect the river to remain high, but our forecasts indicate that flooding to properties isn't likely and therefore flood warnings are not expected to be issued.
"We are constantly monitoring river levels, and have staff in the field checking for blockages and clearing weedscreens.
"Please avoid using low lying footpaths near local watercourses and plan driving routes to avoid low lying roads near rivers, which may be flooded.
"Please do not attempt to drive through flood water."
A similar flood alert — the lowest level in the Environment Agency warning system — is in force in the south of the county for an area around River Tove from Towcester to Cosgrove.
Met Ofice forecasts promise rain for around 36 hours from midnight on Monday night.