Learn Swedish: Kallt väder gör en sjuk. - Cold weather makes you sick.

Man is used when the generic "you" (or "one") is the subject doing the action. Here, Kallt väder is the subject causing the action. Since the generic "you" is the object receiving the action, it must change to the object form, which is en.

Why is the adjective sjuk instead of sjuka if "you" refers to people in general?

Even though the generic pronouns man and en apply to people in general, grammatically they count as singular en-words. This means any adjective describing them takes the standard, singular en-word form.

Why does kallt end with a -t?

The word for weather, väder, is an ett-word (ett väder). When an adjective describes an ett-word, it needs a -t added to the end to match.

I thought göra meant "to do". Can it also mean "to make"?

Yes! Swedish uses göra for both "to do" and "to make". When something causes a change in state or feeling, like the weather making someone sick, gör is exactly the right word to use.