...it's colder than a witch's brass monkey.
For those who are curious as to the origin of the phrase "Cold enough to freeze the balls off a brass monkey," here is the surprising story:
A couple of hundred years ago, warships carried lots of cannon on their decks. Iron cannonballs were stacked, pyramid-like, next to each of them. To keep the cannonballs from rolling around on deck, they were placed on a large triangular brass plate called a "monkey". The plate had depressions in it so the balls would rest securely. However, in extreme cold weather, metal contracts. Brass shrinks a bit faster than iron, so after a while the indentations in the brass plate would become too small to hold the cannonballs and they would dislodge.
Hence the old sailors' expression.
I read this a couple of years ago on the website of singer/songwriter Amanda McBroom at
http://www.amcbroom.com. She wrote Bette Midler's "The Rose" and her father was the late actor David Bruce (remembered for a few 1940s horror films). There are lots of fascinating bits of information on her site (look under "Gossip"), but unfortunately the "Brass Monkey" story is no longer there.
Signor V.