I second ALOHART's suggestion. I would LOVE to have a basically no cost option like that to switch my 20's for 19's! Not only for the choice of having all season tires, but also for the better ride that the taller sidewall on the 19's give you. The 20's "thwack" pretty good on bumps and cracks in the road.
Having said that, I have the 20's with the summer tires and I had no issues driving it this winter in 20 and 30 degree temps. However, if the roads were icy or snowy I left it parked and drove my 4x4 truck.
2014 BMW i3 with Range Extender Engine, Capparis White/Frozen Black, 20" wheels,, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, TurboCord EVSE