This is due to a rare alignment of the sun, moon and earth, which happens every 19 years. Tomorrow morning will see the highest astronomical tide level in 25 years, which could strain the current flood defences in place, particularly if adverse weather conditions should coincide with the event.
Last year during an overlap of high tides and low barometric pressure, flood defences were exceeded at many locations in Wales including Amroth (pictured), Aberystwyth and Penarth.
As this article was written, Wales had ten flood alerts, and a further three that had been upgraded to flood warnings in place, with roads being closed this morning amid fears of defences being overtopped. It is thought that the area most at risk is the stretch of coast from The Gower through to the Wye Estuary. Though the high tide peak will be tomorrow morning (Saturday 21st of February) the threat will not be over, as Britain could be expecting a further five supertides this year due to the rare planetary alignment.