Breakdown of Если Вам холодно, лучше бы Вы взяли с собой термос и тёплые варежки.
Questions & Answers about Если Вам холодно, лучше бы Вы взяли с собой термос и тёплые варежки.
They are capitalized because the speaker is addressing someone politely and formally, like you in a respectful singular sense.
In modern Russian, this capitalization is common in letters, messages, and other direct written communication when showing politeness. In many ordinary texts, you may also see вам and вы in lowercase even when the meaning is still formal.
Russian usually expresses physical or emotional states with an impersonal pattern:
[person in the dative] + [state word]
So:
Вам холодно = You are cold / You feel cold
Here, холодно is not an adjective agreeing with Вы. It is a state word meaning cold in the sense of how someone feels. That is why the person appears in the dative case: вам.
By contrast, Вы холодны would mean something more like you are cold/distant in personality or manner, not physically cold.