Having baby in May, what kind of clothes to buy since they will be a Summer baby?

I will be having a baby in May, so what kind of clothes should I be buying for their first few months? I live in Canada... I know May is still a little chilly but June, July & August are usually pretty warm, espically July & August. Do I even need to get long sleeved sleepers/outfits? Or should I just get t-shirt onesies and shorts & tanks? If I have a girl dresses... haha I don't want my baby to be cold or hot... So I'm just wondering what sort of clothes I should buy since my baby will be a summer time baby it's first few months :) Thanks!