Cold as...

Colder than a well-diggers ass.
Colder than a witches t i t in a brass bra.
It's a tid bit nipple.

Cold as a banker's heart
Cold as a dead snake in a deep freeze
Cold as hell with the furnace off
Cold as an outhouse seat in January

Cold enough to freeze the (fill-in-the blank) off a brass monkey
Cold enough to freeze the stink off (fill-in-the- blank)
Cold enough to make cows give ice cream

...from of "This Dog'll Hunt" by Wallace O. Chariton.