Like the turkey and the tinsel, the Christmas and Boxing Day swims are part of the festive tradition in Norfolk and Suffolk – but how will they be affected by one of the coldest Decembers on record and temperatures barely registering above freezing?

The festive dips, which help raise hundreds of pounds for good causes, take place all along the coast from Mundesley through to Hunstanton and Lowestoft, and always attract a wide range of colourful characters.

But weather forecaster Weatherquest has warned that this year swimmers could be in for a very cold shock – with sea temperatures dipping much lower than usual.

A spokesman said that on December 10 the temperature in the North Sea measured nine degrees Celsius. Within five days, that had dropped to eight.

'We would expect by Christmas for the sea temperature to be around five and six Celsius, whereas normally around this time of year it would be nine or 10.'

That figure is above the freezing level for sea water, which decreases as salt concentration increases, and usually freezes at about minus two degrees Celsius.

However, it is a far cry from soaking up the sun on the beach at the height of summer when the sea temperature off the coast is usually about 17 degrees Celsius. But organisers of the swims have remained resilient, vowing to take a dip in the sea no matter what the weather.

Clive Hedges, who is helping organise the Cromer dip said: 'We are hardy north Norfolk runners, we will be there whatever the weather.'

He said they would also be making sure everyone was safe with St John's Ambulance and lifeguards on standby.

Liz Payne, chairman of Mundesley Lifeboat Friends Commitee, who is helping with the Mundesley dip, said: 'We always try and keep everyone together and the lifeboat crew are on standby and will be in the sea in their wetsuits, and do not let people stay in the water for very long.

'We make sure we keep strict control over it, and afterwards people are offered the chance to get warm and have a warm drink at the boathouse.'

In fact Lawrence Chapman, who is organising the Lowestoft swim, which has been going for 33 years, said it is not the temperature of the sea which causes problems necessarily.

He said: 'Often the sea is warmer than the outside air. The worse bit is if it is particularly windy or the sea is rough.'