Cold enough to freeze the balls off a brass monkey

This refers to the brass balls displayed by pawnbrokers - they aparently also used to have a brass monkey above them - cold weather would force the welding to snap.

I don't think so - it does not tie in with reality at any point other than the brass balls.

Type in Brass Monkey in the Search box at the top for an extensive, invigourating and non agreed set of origins of the phrase!

Cannon balls on-board british ships, which were made of iron, were stored for use on a 'monkey'. The monkey was made of brass to combat corrosion. When sailing through different temperature regions, especially cold regions, the brass & iron contracted & expanded at differing rates & the monkey would warp, causing the balls to fall off.