I reserve sweltering for when you can see the heat waves in the air. It is a great word. New mexico is a weird one though, being high desert, right? Ya'll actually get a wildly cold winter, don't you?

It's said in the same manner as a mild sarcasm. I'm not sure the word for it, but deliberate understatement that specifically plays on it being hotter than 'warm' is.

As far as 20/68 being chilly, to me it's downright hellish. During the summer, we would keep the house temps around 85/30, because you'd be so used to the sweat and heat of the sun that it wasn't too bad with a light fan... and that was in the houses lucky enough to have heating/cooling. The rest just made do with shade and designs that promoted a breeze.

Anyway, as I said, this is a hot climate's weather terms. If you were able to keep the room temperature the same as the outside in spring or autumn, you probably aren't in a hot climate.