Well If he starts to shiver, look unhappy, or move slower/fatigue like symtoms then you know the cold is getting to him.
if he starts to limp or favor certian paws then you might want to check that out.
Id say he should be fine, but if your really worried you could get some booties to protect his paws.

i wouldnt go as far as a little jacket, just cause they llook weird, and marley should have the winter fur by now lol