How hard is the Thorong La pass crossing?
Short answer
Long, cold, and altitude-sensitive — 9 hours of walking from Thorong Phedi to Muktinath with a 5,416 m summit.
— Detail
Most trekkers start between 4 and 5 AM to clear the pass before afternoon wind. Expect very low oxygen, frequent altitude headaches, and snowfields above Phedi. Carry 3+ liters of water, hand warmers, and crampons in shoulder seasons. Helicopter evacuation is available from Muktinath but not from the pass itself.
Sources
TrailSathi route notesManang Himalayan Rescue Association