The lube is what will cause you problems. Leaving a gun in a car to freeze is not a really good idea if you desperately need it to work. Read up on the soldiers who spent some time in the Chosin Reservoir in Korea.
I promise you a frozen Glock will fire every single time.
If you don't believe me, put one in the freezer and try for yourself.
And cars don't get THAT cold.
You can use lighter, thinner lube, if you think it's a concern, but Glocks are used by polar patrols with no problems.