I can't relate to either of these experiences but I am unreasonably invested in the answer.

You might be dying. Idk

Uhh... What?

How strong is the weed you're smoking?

I'm Canadian and I've inhaled my fair share of cold air. I have never heard of such a thing before.

Halitosis

I’ve never experienced that. Breathing in freezing weather smells like freezing weather. Dry, crispy, and icy. My saliva smells nothing like that.

I suspect that you have a sinus or oral condition. Perhaps you might speak to a doctor about that?

Can't say I've experienced this and I'm a Canadian.

I've found it interesting when I go back inside and I can feel the saliva entering my mouth is cold. The saliva gland must get cold.

I don't know what smell you're talking about about, but the extreme temperature might alter how you taste or smell, which may contribute to that.

Do you floss and brush your tongue regularly?

I would imagine it's simply changes in the bacterial biome of your mouth, but I'm curious too. Especially as to why that saliva smell also comes off snails. 🤢

I can agree that crisp, cold air has a taste sometimes. But I would never describe it as milky. To be fair, I’m not sure how to describe sooo

Ozone, maybe?

Does it taste kinda metallic?

My guess is similar to everyone else, that the dryness is affecting it. Cold air might dry things out, especially if you're breathing heavily through your mouth since your nose feels cold (and cold weather can be strenuous). That might cause it to get dryer, or decrease saliva production entirely and make things thicker

This might be a weird thing to experiment with, but that might give you some areas to test out

Synesthesia?

I've smelled the mildly sour smell of saliva on skin, but I don't know if I've ever noticed a specific odor when it's cold.

Wow I didn't know that was uncommon, it happens to me too. I don't have any clue what causes it unfortunately.