Mountain rescuers are urging hikers to be better prepared after a stag party attempted to climb Snowdon in their pyjamas.
The group set out in the nightwear and trainers, but got caught up in a "horrific" storm.
The Llanberis Mountain Rescue Team (LMRT) chairman John Grisdale told the BBC the group set off last Thursday and ended up in a "horrific storm of thunder, lightning, very very heavy rain and quite strong winds".
He added: "It seems as if they had had a very pleasant walk on Snowdon last year and they wanted to repeat the occasion, which I can understand...unfortunately I think it would be best to have left it for another day and had more enjoyment.
"Had something happened, a very trivial thing like a twisted knee or a broken ankle, or something like that, conditions on the mountain meant that they would've been seriously cold, miserable, wet and unfortunately drawing, probably, the mountain rescue team out to help themselves as well."
The warning comes as the rescuers were called out to assist in three separate incidents this weekend.
On Saturday evening a group of 11 had to be talked down the mountain after getting lost in mist.
Mr Grisdale added: "In the course of six hours we dealt with three separate incidents.
"It's hardly surprising. The pressure of people on the mountain is extremely high.
"There are now often large groups of people on the mountain, including sponsored walks.
"Many of them are poorly equipped for the conditions.
"We have come across organised groups who are going up in T-shirts and jeans rather than supporting best practice.
"There are some that have best practices but some have a lack of understanding of the mountain conditions which at this time of the year can still be cold and wet.
"They need to be better prepared for the weather, with winds and lots of rain. The temperature is quite low as well.
"Being prepared is a significant part."
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