Northern and Southern California are so different they could probably even be their own states. Here are a few differences I've noticed through living in Southern California but visiting my older brother in Northern California pretty often.
1. Driving speed
Northern: Going the speed limit of 65 mph makes you feel like you’re flying
Southern: Going the speed limit of 65-75 mph has drivers honking at you and aggressively speeding around you because everyone else is going 85 mph (road rage is very real)
2. Beaches
Northern: where going to the beach makes your limbs feel numb
Southern: where the beaches are fairly warm year round, but especially in the summer months
3. Seasons
Northern: where you see leaves change colors, you feel crisp fall and winter nights, and you definitely need a rain jacket and rain boots in the winter time
Southern: where you can still get away with jeans and a t-shirt and maybe a wind breaker for two days out of the entire “cold” season
4. Greenery
Northern: where hills and mountains are covered in lush and green shrubbery
Southern: where hills are mostly dirt and dust
5. Political Parties
Northern: where you will mostly find Liberals
Southern: where you will find a lot more Conservatives than Liberals
6. Types of People
Northern: where you will find laid back, genuine, down to earth people who can also be a little hippie-ish
Southern: where people tend to be more rushed, but also very laid back and friendly
7. Attractions
Northern: where you will find the beautiful big city of San Francisco, Wine Country, and world famous breweries
Southern: where you will find another big city, Los Angeles, but not quite as busy as San Francisco, accessible beaches all along the coast, and the famous Disneyland and California Adventure
8. Food
Northern: where you will have the best seafood you’ve ever tasted
Southern: where you will have the best Mexican food you’ve ever tasted