Dry scalp or dandruff?

i've never had flakes in my hair until i went off to college. i grew up in hawaii where it is VERY humid and very warm all year round. once i moved up to canada, my skin went crazy and became severly dry due to the lack of humidity and i have flakes in my hair now! i don't know if its dandruff or dry scalp. its itchy,and sometime scabs, and flaky and is supper bad when i'm up in canada. when i come back home to hawaii it goes away after a couple of days. do you guys know which it is??