I have a senior rottweiler (he's 11). I've noticed this year he's been expecially cold, to the point he shivers We bought him a heated dog bed, not a really big nice one or anything, this one, we just laid over his old bed.
Here's a pic of it:

We've also covered him before, but now with the bed, it seems like he is most comfortabe
Here's one before we got his bed:

And one after we got it:

I think he was so comfortable he drooled all over

I don't know if Angus would wear any sweaters or anything, I've never tried, but it's a thought!

Hope you can keep your boy warm this year!