Learn French: En hiver, il neige beaucoup. - In winter, it snows a lot.

Yes, you can! Pendant l'hiver means "during the winter," which focuses on the duration of the season, fitting with your current lesson on closed durations. However, en hiver is the standard and most common way to say "in winter" when stating general facts.

Why is it en hiver? Do we use en for all seasons?

We use en for seasons starting with a vowel or silent h: en été (in summer), en automne (in autumn), and en hiver. The only exception is spring, which starts with a consonant, so we say au printemps.

Why does the sentence use il (he) for the weather instead of a neutral word?

In French, weather expressions always use the impersonal pronoun il, exactly like the dummy "it" in the English phrase "it snows." You cannot use ça or ce here. You will also see this in phrases like il pleut (it rains) or il fait froid (it is cold).

I thought beaucoup was usually followed by de. Why is there no de at the end of this sentence?

You use beaucoup de when describing a large quantity of a noun, like beaucoup de neige (a lot of snow). In this sentence, beaucoup is describing the verb neige (snows). When beaucoup describes an action rather than a noun, it stands completely alone.