in terms of how low it can get I would imagine it will be fine pretty well as low as you could get it, as long as there was no moisture in there. It's only higher temperatures that are harmful to electronics as far as I know.
I'm pretty sure 0 Celsius may be the lowest it can work at? I dunno though... you could protect it from the cold by wrapping it in a wool sock (no joke). It shouldn't degrade the signal and would help it stay a bit warmer?
Interesting...I will definitely try the sock when snow starts falling. Surprisingly, moisture hasn't been an issue. I keep a little hole open at the bottom of the bag to "equalize" thing a bit. 0 Celsius is not the lowest it will work, currently it is running without issue at -5.5 Celsius A.K.A. 22 F.
NICE! However, I would SEAL the bag as much as possible with a teaspoon of rice in the baggy (to neutralize any moisture that sneaks in!).
I have had my wireless USB network adapter hanging outside my window for over 2 months and the lowest temperature It reached was -5 F. It performed flawlessly through the "polar vortex" blizzard we had in buffalo NY. 2 feet of snow and rain the next day, no issues whatsoever. I did have to blow some snow off of it because it was affecting the bandwidth a little. Other than that no issues at all, and I only used one sandwich bag with some tape back in the summer to protect it. Amazing