+1 discretion is the better part of valor, when it comes to winter riding.

Here in the metro NY area, winter temps swing back and forth through the freezing mark daily. That means that snow melts and the runoff sheets across the road (on hills) during the day, then refreezes in the evening. Since I come home in the dark, so-called black ice is even easier to miss (though I try to remember the places prone to it). Even with studded tires, it's easy to be surprised, but even if ready it does me little good if I can handle it but the car behind me can't.

So my rule is simple, no bike commute if there's ice on the roads. I save my ice riding for frozen lakes and golf courses.

BTW- another ice warning northern cyclists should be aware of. "Bridge freezes before pavement". When temps are only slightly below freezing, pavement may still be warm enough to thaw sleet or freezing rain. But overpasses cool fairly quickly to air temps and will ice up while the road doesn't. A nasty surprise for those not ready.