Brothers Rory and Leon Probert spent hours in appalling weather before rescue crews arrived.
The pair, from Pontypridd, Mid Glamorgan, decided to head for a cabin on the summit.
Rory, 18, said: “We thought ‘we need to get to the summit or we’ll die’.
“We were wandering about for ages and we were hallucinating.
“We got in the shelter but it was still freezing cold.”
Near the top Leon, 31, managed to get a phone signal and alert police.
Lochaber Mountain Rescue Team, who picked them up on Sunday morning, said they were “lucky guys”.
Rachel Slater, 24, and Tim Newton, 27, from Bradford, are still missing on the mountain after nine days.