Whether to capitalize north or south or northern or southern can seem complicated. Why do we say north of the lake but meet me in the North, or northern winds but Southern Hospitality? As with most things in the world of grammar, there are a few rules to help us out.
Rule 1: Capitalize north, south, east, west, and their derivatives when belonging to proper names or when used to signify specific regions: I live in the North, North Pole, Southern Hospitality, West Coast, down South.
Rule 2: If the words indicate a direction, do not capitalize them: I lived in the south of Germany, drive west on this road until you hit the stop sign.
Rule 3: Capitalize northern, southern, eastern, western when referring to people of a region, or of political, social, or cultural activities. Lowercase otherwise (e.g. climate or geography): Easterner, Southerner, northern temperatures, Western civilization, the Northern vote, the northern climate is cold. Notice that the political northern has been capitalized, but the climate northern has not.
Rule 4: If preceding a location, lowercase the attribute unless it is part of the name: northern New York, Northern Ireland, western Germany.
You might have noticed a trend among these rules: capitalize proper adjectives and lowercase improper adjectives. Allow me to explain; proper adjectives have more class, money, and refined manners. In other words, proper adjectives are ones that refer to or belong to nouns. France is a noun, and French is a proper adjective, because it refers directly to the preceding noun. I lied about the manners.