Communities in Maldon, in Essex, are being advised to move pets to safety, avoid coastal paths and promenades, and postpone road journeys where possible.
It comes as the Environment Agency issued flood warnings for Norfolk, Suffolk and Essex.
High tide is expected in Maldon just before 5pm.
The Environment Agency is warning that businesses and homes alongs the waterfront and The Hythe could be at risk.
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Cloudy, humid at first, with thundery showers dying out.
Cloudy, humid with occasional rain, sometimes heavy and thundery.
Temperatures soared and the sun shone but there were also some torrential thunderstorms - a typically mixed Bank Holiday weekend.