Hardy fans of swimming in the frozen lakes of northern Poland have decided to call off a mass outing this weekend due to vicious cold snap gripping the country, organisers said Friday.

"In the interests of our participants' security, we've decided to call off this year's Bath of the Brave," Ireneusz Dzienisiewicz told Poland's PAP news agency.

This year's edition of the annual swim in a lake near the city of Elk -- which draws around a hundred participants -- was due to take place on Sunday.

But temperatures in northern Poland have plunged to minus 30 Celsius (minus 22 Fahrenheit), far below the minus 15 Celsius experienced by swimmers in 2010 during the coldest ever edition of the event.

On top of the risks to the swimmers, there were also practical reasons for cancelling the event.

"The water freezes so fast that we wouldn't be able to keep a large enough hole in the ice," said Dzienisiewicz.

Since the cold snap struck Europe at the end of last week, 37 people have died of hypothermia in Poland, according to the police. Most of the victims have been homeless.