So, if you wait for the snow to fall on the ground, how do you get your car to the garage without breaking the law?
Tell me you've never lived through a single snowy season in your entire life without telling me.
You have three options: Preempt the entire season, and throw your tires on in September or October, instead of waiting until November. Or, when the first light snows begin, drive to the garage while conditions still permit it. Or, if caught by surprise by a heavy early snowfall, wait it out, then drive to the garage once conditions are again favorable, and before they become unfavorable for the rest of the season.
The text of the law linked upthread clearly allows for driver discretion during the legally-mandated snow tires period, unless conditions require snow tires. It follows that the law recognizes that conditions may vary from place to place and time to time during the period, and that the law expects drivers to make their own determination as to when snow tires are required for the driving conditions they anticipate.
Honestly, the law seems poorly worded to me. If the requirement is calendar-based, then driver discretion about driving conditions should not be permitted during the legally mandated period. On the other hand, if the requirement is condition-based, then it should be in effect year-round, not restricted to an artificial calendar "season".
My guess is that the law is intended to give drivers full discretion as to driving conditions and snow tire requirements, while still providing a legal basis for telling drivers they should know better, if harm arises from them driving without snow tires during the depths of winter.
I can easily imagine a Finn in midwinter, driving from his urban center home to his urban center garage, where the streets are plowed and de-iced and the conditions are fine for non-snow tires. And I can imagine him getting snow tires put on at the garage, in preparation for his planned drive out of the city, over the river and through the woods, to his winter cabin or relative's home or somewhere else where he anticipates snow tire conditions.