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.