Last winter I had to change in a flat in the and with freezing rain. I kept screwing up, went through two tubes, so it took like 30 minutes and absolutely sucked. On the other hand I've changed flat in cold rain in five minutes.

I think if you can do it confidently and quickly, most roadside repairs can be done in subfreezing temperatures and nasty conditions. If you're not sure about your abilities to do it quickly, then yeah, a bailout or just taking the bus is probably better.