Boston Terrier Breathing Problems

I know we have some BT fans on the forum, so here goes..

Our little female is about 4.5 years old. I'd say her breathing has been typical for the breed (including occasional reverse sneezing and occasional very heavy and prolonged panting after a lot of activity and excitement). She is otherwise healthy. Good diet and weight.

But this is new. Out of the blue, as soon as she breathes in cold air, she starts to labor a bit. She barely will stay out long enough to pee, and really doesn't want to stay longer for number 2. When she gets back inside, she's doing the reverse sneezing sort of thing for a while, and of course looking up at me with big, watery BT eyes.

After the spell is over, she back to normal, but I have concerns that it could be something serious, and as often happens with pets, this worrisome situation started right outside of normal vet hours. Oh, and we've got about 4-6 inces of snow on the ground, and we're in the middle of another 1-3.

So, anyone have similar experiences? Anything I might be able to do until we can get her in to the vet? Thanks all.