I usually chose 1/4" Manilla because it shrinks when it gets wet, and our orders were to make our lashings 'tighter than tight'. However, none of our knots slipped when they froze. They froze in place, and held just fine.
We had the same results with synthetic line. We never worried that any knot would slip when frozen. As a matter of fact, the fishermen among us had a particular knot for lashing the bag of a net, so they could untie it when it was frozen. It was a slipped knot, and the bitter end had an eye spliced into it. They put the eye on a strap with a hook, and ran that to the winch to break it free, dumping a load of fish on deck.
Running Feather, I predict that you will hang safely all night long!