"Cold enough to freeze the balls off (or on) a brass monkey" is a colloquial expression used by some English speakers to describe extremely cold weather.

The Brass Monkey is a cocktail made with dark rum, vodka and orange juice, sold as a premixed cocktail in the 1970's and 80's. It was sold by the Heublein Company, which later dissolved in 1998.

In the days when gulf wars had more to do with sailing ships than TV coverage, cannon balls were stacked on the decks in pyramids. The pyramids were held in place by a brass frame around the base, called a "monkey". When it got cold, the brass monkey contracted, and the cannon balls rolled off around the ship's deck.