I also go by the "one layer more" rule.

But it does get really really stinking hot here and if it's 35 degrees I'm not putting a singlet under his clothes! Usually then he just wears a t-shirt and nappy, or singlet and nappy if we're at home.

I find night time really difficult to dress them - it can get sooo hot here at night but early mornings are still quite cool...it's a constant drama LOL.