Variables I can think of that change:

- Lane lines cease to be a thing, even if you can see them, you're better off not following them

- Stoplights also mostly become a guideline, it's sometimes safer to run them than spin out

- Signage or signalling may or may not be visible at all

- Other cars or pedestrians may or may not be visible at all even in daylight

- Your stopping distance can effectively change every few feet

- A foot of snow accumulation may be transferred from the roof of the car in front of you to the windshield of your car with little to no warning