asterisk8 said:
It doesn't look warm and toasty inside Echo Base, probably -12 degrees Celsius. So my question is, at the threshold of the hangar door, would the -32 degree air meeting the -12 degree air produce any kind of visible water vapor, or is it too cold?

The "mist" that you can see when you exhale into freezing air is light reflected off ice molecules that have just been formed from the previously liquid water of your breath.

For this effect to occur, the water must have a temperature above freezing to start with.

This would not occur in Echo base because temperatures are below freezing both inside and outside the base (C-3PO said that it was freezing even in Princess Leia's private chamber, remember ... )

Also, air humidity decreases with lower temperatures. Cold weather that is below -5 degrees Celsius is always very dry.