Winter hung its head yesterday as Marlburians thumbed their nose, stripped off their clothes and plunged into chilly waters.

In Picton, 350 chill chasers plunged into the harbour at 1pm, in the annual Sounds FM Midwinter Swim.

They entered with shrieks and emerged with smiles, to be warmed by hot water sponsored by Montana and sprayed by the Blenheim Rural Fire Force, and cheers from hundreds of onlookers.

At Lake Rotoiti, 20 hardy souls plunged into the icy waters, far colder than those at the seaside.

St Arnaud man John Wotherspoon said all stayed in for 30 seconds, but half a dozen hung out for five minutes in the freezing water.

He's done it the past four years and said this was the coldest yet. "It was a really frosty morning. My feet stuck to the stones coming out of the water."

Midwinter Swim Sounds FM promotions coordinator Bridget McNamara said the Picton event was another great family day, with gorgeous sunshine a more than welcome break from last week's winter blast.

The top spot prize of an inverter Heat Pump from Cuddon Ltd in Blenheim, valued at $3000, went to Renwick man Danny Giles, who sauntered up in a towel to accept it.

The draw was random but well won, since Mr Giles was seen strolling through the water prior to the swim, and lounging about in it long after, while most others were huddled on shore in warm towels.