Learn German: Im Winter schneit es viel. - It snows a lot in winter.

In German, all seasons are masculine nouns, like der Winter or der Sommer. When you want to say "in" a season, you use the preposition in plus the dative article dem. These two words always combine into the short word im. So, you are literally saying "in the winter".

Why does the verb schneit come before the subject es?

This is the "verb-second" rule in action. In German main sentences, the verb must always take the second position. Because you started the sentence with the time phrase Im Winter in position one, the verb schneit must come next. This pushes the subject es into position three.

Is es used here exactly the same way as "it" in the English phrase "it snows"?

Yes! Just like in English, weather verbs in German need a subject even though there isn't a specific person or thing doing the action. You use the impersonal word es (it) with the verb schneien (to snow) to make es schneit (it snows).

Could I say viele instead of viel in this sentence?