I haven't seen a random table that needs to be rolled that uses a modifier, so I really liked that you choose to roll STR because it's a STR-based activity to climb the mountain. Super clever.
The cold weather rules also really made sense to me. But the rest was very hard for me to understand, when do I encounter what and how? Sorry. It's probably just me. But it lacks a little.
Your rules and tables are really on fucking point though!