Making the safe decision (AKA "I hate AIRMET ZULU")

It's important not to forget the other side, where the freezing level
is (figuratively) far underground. Once you're looking at surface
temperatures of -20 degC or lower and no inversion aloft, icing becomes
very unlikely. You're not likely to have low surface visibility in
that weather (except for blowing snow), but mid-level ice-crystal cloud
might still be below MEAs enroute if you're passing over hills. We see
fewer winter days like that, though, with the rising temperatures.