I feel the whole penalty system feels way too harsh. The idea of implementing a weather system is a thing that would make the game unique but also feels like it is not needed at all in the game. Just the month before the weather system i had fun playing the game and the weather(especially cold) at some regions just destroys the fun of playing the game for me.
I agree it is intended that you might want to equip the right armor for the right biome which might solve the negatives. But let us look at it from the viewpoint of a new player starting the game:
Starting with T1 armor you wont have good resistances. You and your group (which you kinda need if you are completly new) started in aerhen and now as soon as you go to any area in the region you feel kinda overwhelmed. At night in colder areas you get up to 99 chilled stacks and are almost unable to move. At the fire elementals they shred you and you wont have a lot of fun fighting there. So they come to the realization - this area is too hard lets find something easier so we can grogress that area when we have better gear/skills.
If you dont know nothing about a game you die quite a lot even against a small pack of wolves. The weather features on top of that kinda are forcing the game in a super hardcore direction. I dont think you can get or hold a big player base in such a hardcore game.
So lets look at the weather feature out of the viewpoint of an older player:
You get yourself a build together and you kinda have to do quite some management for your mana for your build to kinda work (at least in the current state of the game). So what you do is optimize your gear around mana management and maximizing evasion, block and armor since they seem to be the strongest defensive mechanics. So you will be left open with like one really good set that works with your current build. Now all this just gets destroyed with the weather system. One build might due to slowing not work at all in the Jotunn area. Just because you get so many cold stacks you feel like you are an immovable rock. The only workarounds for it is a spell channeling weapon + protection from cold - if you can sustain the extra 20 mana per second (which also might destroy your build) or destroy the current build and play something completly different from what you think is the most fun just to be able to wear mammoth wool clothes which will help in cold areas.
Just a testing example for you the current cold area:
Play a meele build with any plate armor because you want to be able to tank a jötunn and not cheese the reset mechanic. This armor set will reduce your max speed because it is plate - so it already feels really slow. And now add 99 chilled stacks which are ~50% reduced movementspeed. As a tank walking from one mob to the next one just takes a minute - fun gameplay!