I was running a fairly short campaign (maybe 5 sessions). I didn't find that the extreme weather conditions are as deadly or lethal as the party levels, but maybe that was my 'fault' because the weather was more of a challenge than the threat. I think in a setting with extreme weather having a woodsman/ranger helps immensely, as does having various casters. I think parties might 'age out' of the weather's lethality as it were.
For useless background, the premise was: A meteor crashed into the planet, causing an impact winter. It became a points-of-light style game, and my party found the cultures I'd modified for the world the interesting aspect (for example, halflings were largely dead as a culture, having held off barbaric hordes, post-crash, through their use of firearms from the gnomes. The players discovered, when they were sent to recover whatever remained of halfling lore by the leader of the last 200, that halfling 'magic' was in cooking - they had invented Heroes' Feast as a spell, the players found a lemon cake of halfling craft that gave frost resistance, etc) ... Oh, the meteor? Actually was the corpse of Ymir, crashing through various planes until it landed there, having brought some unknown viral creatures with it... YMMV