Our Boy’s first Winter – Any tips?

We got our boy in March. He’s a rescue from Texas, but was brought up to a northern state. This week has been our first taste of truly COLD walks. Our dog is a 65lb, double-coated, and about 15 months old. We don’t have a backyard, so his outdoor exercise is gonna be mostly walks. We are committed to giving him the 90-120 mins of walks he needs, but I would love any advice you folks have on:

1) what signs should we be looking for to see if he’s cold and needs the walk to end?

2) what can we do to make walks in the cold more tolerable for him?

3) what can we do to make walks in the cold more tolerable for us?

Thanks in Advance!