mommamia:
Is it, in fact, a mitzvah to wear it all the time, or only to “add” it to a four cornered garment, when worn?
The mitzvah is to put tzitzis on a four cornered garment. But you get a mitzvah for wearing them all day. If I go up to the North Pole then I guess I would not be mechuyav in wearing tefllin the whole 6 months that the sun was down. But why would I want to give up that mitzvah?
Speak to your Rov. Maybe your son can hydrate more to counter the strong heat instead.
b_o_r:
it makes little sense to dress in layers no matter how stong you want to show your faith to be.</em.
From this statement, it occurs to me that you might not know that the purpose of wearing tzitzis is not about showing your faith to the public but about a Biblical commandment to wear them, regardless of whether you’re a hermit or gregarious. Maybe I misunderstood your meaning here…