A helicopter was unable to rescue the climbers because of turbulence

The two men and a woman, from the Caernarfon area, were said to be ill-equipped and ill-prepared and only began the climb at 1800 BST on Sunday.

They had not reached the summit when darkness fell and they became trapped on a steep section of the Pyg Track.

Llanberis MRT brought the uninjured walkers down to safety by 0145 BST.

The trio - aged between 18 and 21 - had intended to visit the now demolished summit cafe before descending to Llanberis, but had not seen signs at the bottom of the Pyg Track indicating the cafe had closed.

When darkness fell, the walkers were trapped and called for help on a mobile phone at around 2200 BST.

As always, preparation and planning are crucial Dr Gwyn Roberts, Llanberis MRT

A Sea King helicopter from RAF Valley was able to locate the party using a thermal imaging system but was unable to land or winch them to safety because of thunder in the area.

Rescuer Dr Gwyn Roberts said the walkers were poorly-equipped, wearing jeans and sweatshirts. They had no torch or shelter and were cold when the rescuers got to them.

"Llanberis MRT would remind walkers that despite the warm valley weather recently, conditions on Snowdon can be very different," said Dr Roberts.

"As always, preparation and planning are crucial.

"Some experienced walkers do begin ascending the mountain at this time of day when the weather is good because the paths are quieter. But they are always well prepared with spare clothing and torches."

Dr Roberts said "prominent" notices were displayed at the bottom of the paths on Snowdon warning that there are currently no facilities at the summit.