I have several boys and girls of wildly varying age. When we had our first child my wife and I thought that differences based on gender are all due to the environment, and that we would never let this happen to our children. Now, several children later, I laugh at this.
One of the things that set my boys apart from my girls is that the girls consistently act responsibly at a much earlier age than the boys.
A five year old girl realizing on her own it's cold and she should get other clothes from the wardrobe seems a year or two younger than my girls started to deal with them on their own, but I could very well imagine this. Contrary to this, none of my boys were very well in this at the age of seven. In fact, they probably weren't at nine or even ten. (OTOH, the child currently making the most fuzz about what to wear is my teenage boy. To him, this is at least as important as for his older sister. So this could improve.)
I work hard at handing responsibilities for their life to my children as early as possible, and I let them do and decide things at an age where others just shake their heads about me. But this ultimately depends on the child, and there are huge differences between boys and girls, but also between different boys or girls. One child would make a train journey alone at the age of 8, another only at 11. One child stayed home alone with two younger siblings to care for at 14, another did that at 11. (Just to counter my own argument: the latter was a boy.) I left the decision when to turn off the light, stop reading, and go to sleep to some of my children at the age of 11, but I seriously doubt that I can do this with the child that is currently approaching this age.
You see where this is going: No two children are alike. (In fact, I often say that the one thing that all of my children have in common is that they all have very different personalities.) I am all for encouraging children to be more responsible, but which decisions, tasks, etc. are left to them at what age is a highly individual decision that depends mostly on the child.
So how do you actively encourage independence?
I found that this starts very early, by not simply making decisions for a child, but involving it in the decision-making, explaining the reasons why you would decide the way you do, and being open for suggestions from the child. This absolutely includes letting the child make mistakes, even when they hurt a bit. (I don't see my task in preventing my children from every possible hurt, getting scratches and bruises. I see my task in preventing them from permanent harm. This has the advantage that my children know from experience that what I suggest is often what they should do, and thus follow my council voluntarily. In fact, the best way to end a discussion whether the warmer jacket should be worn to school is to say produce my arguments, and when they don't give in, to say I am fine with it, I said my piece, and they can do what they want. Left to their own device, they usually follow my advice.)
If you try to always do this, then it comes rather natural (for both sides involved) to let the child have more and more influence on the decisions made when it gets older and acquires a firmer grip on how the world works.
In your example this approach might involve talking with your son about what to wear (and why) every day. For me, there's many things that influence such a decision (whether, expected activities, what's currently in the laundry or should go there, and whatnot), so it's rather complex for a child. However, constantly being involved in juggling those factors eventually teaches juggling.
How long that takes, however... see above.
