99.9%? I'm not an expert on climate, but I would guess that at minimum 50% of the world faces snow or fog or heavy rain while driving at times. In some places, 30%+ of all driving year-round could be in snow-inclusive conditions.

99.9% of driving of sea-level, non-rainy, near-the-coast California/Austin weather, maybe. I would guess it's a no-go in the inland foggy conditions in CA, for example, or freezing rain in TX.

In terms of ALL conditions? 60-70% maybe.