Moving countries has ruined my scalp health

I moved to Australia 3 years ago and my scalp and hair is still struggling to adapt. I am from southeast Asia, and very used to the humidity and hot weather but now that there are seasons, my scalp is just always so itchy and dry, yet looks super greasy.

Is it the water or the air? I used to use any brand and I wouldn't have an issue. Do I need to use different products in each season?