A flood alert has been issued for the area that includes Brighton and Hove as gales of up to force 10 have been forecast.
The Environment Agency said that flooding was possible for coastal areas from the western arm of Shoreham Harbour to Beachy Head.
The agency said that low-lying land and roads would be most likely to be affected first.
It said that at Shoreham, for example, high water was due just after midnight with surges expected.
Storm force southerly winds of more than 50 knots have been forecast with south westerly waves.
The agency’s duty officer can be contacted through the Incident Communication Service on 08458 503518.
