Are you wearing your tinfoil hat at the time or not? It makes a big difference.
Seriously, I'd say a lot depends on what you're wearing, your weight, how hydrated you are and a bunch of other variables like how close to an atmosphere you are, how close to expended rocket fuel you are (and how hot that is), if there's any sources of radio activity, etc.
If you're naked on the dark side of the moon and completely in shade, I'll guess that your core temperature well below 0C in an hour. If you want more specific, I suggest you look for information on liver temperature readings after death. I'm sure that there are studies that you could at least extrapolate a close enough answer.