The devs said that the Blizzards and Dust Storms currently do not provide any bonus yields, because they couldn’t come up with a bonus that made sense.
The original argument with dust storms when they announced them was something like, fertile soil is moving from one place to another. I'm not super miffed about it because plains and grassland are the highest base yield tiles at +2, so you want to be on them anyways.
OTOH, blizzards are purely a penalty now for a biome that's already bad (tundra.) Blizzards/snow storms actually have some positives for crops.
Some of the most fertile soil in the world lies in the US upper midwest, which, if you didn't know, gets absolutely
pounded by extreme low temperatures and snow annually. Southern Minnesota-Iowa-Illinois is 200 bushels per acre corn country over millions of acres. IIRC these numbers demolish european farms, which has a
much longer season of "it's not frozen," the primary limit on harvest time.
Getting an extra cold winter storm or two helps kill off insects for the next season, it can help soil in a few ways (deep freeze /thaw helps loosen the soil, and it helps soil retain nitrogen longer) plus snow cover itself can help protect the buried plants from cold weather. If -40 temps and several foot blankets of snow actually did bad things for farming I'm pretty sure we would know.
The main reason I want blizzards to drop some fertility is that it would open up canada and russia to some really fun gameplay.