The Environment Agency says we should "be prepared" after issuing a Flood Alert for the Eastern Yar.
It says flooding is also possible for tributaries from Whitwell to Bembridge - as the water level is expected to rise.
In the last 18 hours, 15 mm of rain has been recorded at Wroxall.
From midday today (Thursday) the river will be high at Langbridge and Alverstone.
This is expected to cause 'minor impact flooding' to low lying land, footpaths and cycle tracks.
At Alverstone, the river is unlikely to peak until around 3pm tomorrow (Friday) due to heavy rain overnight.
The next update is at midday tomorrow.