The fact is it's a complete unknown. On a PA28, you could probably get away
...with none.
It's quite well known.
Airframe ice and winter flying are only somewhat related. My worst experience with ice had us falling 6000 feet, in control, at maximum power, and below best rate climb speed. It was August, over the south of France. We fell to warmer air, and continued on, much the wiser.
If you are flying VFR, and encounter ice, and turn around to exit at the first sign, you will be safe. Other than that, this is a whole different discussion, and not really centered on winter flying.
Anyone who intentionally continues flight in icing conditions in a non equipped aircraft is a fool.