That's awesome that you're going to Chile to study! I plan on doing the same next year for my junior year :)
What school will you be studying at in Chile? I'm a native Chilean so I know almost every school down there. Depending where you go you will see different things.
I have a feeling you will be studying at a school in the 5th region...maybe in either Viña Del Mar, Valaparaiso, or Santiago? Those are the cities where most colleges are located.
Either way...the 5th region has a lot to offer.
Viña Del Mar: Some of the most amazing beaches and night life. Definitely go out when you are there! Clubs like Scratch and Kinki Beach were some of my faves! The music festival is held there every February and that's something you don't want to miss....artists like Daddy Yankee, Nelly Furtado, Franz Ferdinand and others have performed there and it's just an awesome thing to go with your friends. Go one day with your friends to the horse racetrack...its a great way to spend a sunny spring day. The Casino is also right by the beach or take a stroll on a horse and buggy like in Central Park :) I know the ATP Viña Del Mar tennis tournament was held in Viña until last year when they moved it to Santiago...but make sure to catch that if you are a tennis fan and see Fernando Gonzalez play!
Valparaiso: You can visit the "asensores" located on different famous hills around the town, like Cerro Alegre and Cerro Barón. Visit Pablo Neruda's home...it's like a museum and you can learn a lot more about him. There are also a few trolleys left around town so definitely take a ride in one of them. Visit the port and just see the beauty of the street markets and the ships. Go to a seafood restaurant and enjoy some of the best seafood in the world!
Santiago: Most cosmopolitan city of South America! Make sure to visit all the museums there! Definitely go visit the tallest skyscraper of the country that was just inaugurated there...Visit "La Moneda", which is like The White House of Chile. Go to the clubs there! There are wineries nearby so go wine tasting for a day :) Do some shopping in "Patronato"...you will always find sales there on anything! The national stadium is in Santiago....so make sure you catch a soccer match there since Chile is a soccer crazed country and we're going to the world cup this year....there will be a lot of matches going on there.
I'm sure there are a lot more thing to do in these cities but these came right to my head. Also, The Andes mountains and resorts like Portillo are not to far so you can go skiing or snowing for a day or two there. Don't miss the rodeo...which is like a national sport for us. There are a lot of camping and things like that also....make sure you do all these things to get the full Chile experience! :)
The seasons are the opposite from the U.S. So when we have summer, Chile is in winter. When we have fall, they are in spring. It's like that with all the seasons... and the weather is a lot more milder than here. It usually doesn't snow...so it doesn't get below 20's like in NY during winter time....and during the summer the hottest it gets is about low 90's..and that's an extreme, and is not humid like here, so you don't feel all sticky and sweaty during summer time :) But this is for the central part of Chile....The North is usually drier as the Atacama desert is up there and down south is a lot more rainy and cold...so it depends where you are going to.