The 265/35R-21 will fit the front. The front wheels are 9.5" wide, the rear wheels are 10.5" wide, so the 265/35R-21 may not fit the rear. There are many threads that cover this topic. Your best option may be to purchase a 19" winter wheel and tire package from Tirerack.com, TSportline, or Tesla (currently Out of Stock, Tesla has a caveat that the 19" Gemini wheel and tire package is not compatible with the Performance Model Y but many Performance Model Y owners have fit the 19" Gemini wheels, tires to the Performance Model Y with no fit issue.)