Unless you had pure water in the motor antifreeze is good to -34F if mixed right.
I'm in PA and have seen temps to -10F in my garage... all the motors there have 50/50 in them and are fine.
If you did use water.... that could be bad. With any luck the cold shrunk something that was marginally watertight (like a clamp)and that leaked.
Please post back what you find.. it would be interesting to see what exactly happened.
