A charity climber developed hypothermia when he tackled Snowdon wearing just his underpants.
19-year-old Nathan French wore Superman underwear when he climbed the mountain - the highest peak in England and Wales - in aid of a dementia charity, the Daily Telegraph reports.
He became unwell because of the cold and required medical treatment. Now mountain rescuers are urging other climbers to make sure they wear appropriate clothes.
Phil Benbow, of North Wales Mountain Rescue Association, told the BBC that a "significant number" of calls were received each year from people who are not equipped properly.