ColumbiaMen's Hart Mountain Ii Hoodie

Is this for colder weather or is it lightweight?

I am 5'10'' 185lbs what size should i get ?

I'm 182 cm and 50 kg (yes very thin!). I'm normally wearing small, but most comments here make me question my choice (medium maybe?) What's your take?

My son is 5'6 and 125lbs. What size would be best for a comfortable roomy but not tight fit?