Just leave it for now and go back and try it when you can,it will sort it's self out soon,that is the easiest route,you could try pumping the brake pedal on and off quickly a few times while you hold the handbrake lever up,when it's free as Nigel said park in gear no handbrake just now,your only suffering from severe weather at the moment.Good luck it will warm up soon.
Rich, January 2010