The Environment Agency says it is closely monitoring weather forecasts as the Met Office predicts heavy rainfall across the south.
There are currently 55 flood alerts in place across the region and river levels are expected to rise over the next few days and through the weekend.
Rain will continue to move through the south east this afternoon with up to 8mm expected.
Many rivers remain above their usual winter levels following recent snow and rainfall, and ground is already saturated.
Residents are being warned to prepare for further flood alerts to be issued as rivers react, particularly across Hampshire and into Berkshire.
Low pressure will continue to sustain a moderate to large swell and high waves are expected, mostly affecting the Isle of Wight.
Environment Agency teams are also out in Shoreham, Lancing and Seaford reinforcing the shore line defences.
Alison Baptiste, coastal risk manager, said: “Now is a good time for anyone who lives in an area vulnerable to flooding to think about the precautions they can take to protect their properties.
"We strongly urge people to sign up to flood warnings and keep a close eye on local weather forecasts.
"We also ask that people stay safe, by staying away swollen rivers and not attempting to drive through floodwater or taking their boats on to rivers.”
To sign up for EA warnings click here.
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Thursday evening's weather for the west of the region
Thursday evening's weather for the east of the region