What should I wear for snow, or ice and how do I know if I would encounter those conditions? Before covid, when I commuted, I used to cycle in 11 miles each wa

What should I wear for snow, or ice and how do I know if I would encounter those conditions? Before covid, when I commuted, I used to cycle in 11 miles each way every day. Except when the temperature dropped below 5c. Not because I didn't have warm clothes, but because once I hit some ice under a bridge travelling at ~20mph and came off. It took a long time for the wound on my knee to heel from that.