Residents in Southend and Shoeburyness have been put on flood alert as a storm surge combines with high tides.
So why does this weather pose such a danger?
- What is a storm surge?
A storm surge is a change in sea levels. A low pressure system, moving north to south down the North Sea, has caused sea levels to rise while strong winds around that system have caused water to pile up.
This has created a concentrated "bulge of water" which is moving towards Britain.
- Are storm surges common?
Storm surges are relatively rare, with the last major one reported in December 2013.
But it is the combination of the storm surge with the highest tides of the month and strong winds which is putting the east coast at risk of flooding.
- How long will the storm surge pose a threat?
It is expected that the greatest risk would pass after the second high tide - around 6pm in the North on Friday through to 7am on Saturday on the south-east coast.
Mr Snell said the band of sleet and snow moving down the east coast would ease on Friday evening and the lighter winds would reduce the threat.