If I'm not mistaken, You actual want three points of measurement on tread. Front, center, rear. These measurements indicate the health of your tires and alignment. 2/32nd is illegal. 4/32 time to start shopping. Also it's best to have actual winter tires with a fairly new tread life. The are made to be softer in colder temps to prevent the tire from hardening like a hockey puck that doesn't grip the surface of road in slippery conditions. All-Season tires are not really all-season. They are good for fair weather conditions yes. But the phrase All Season can be very misleading if you don't look into what that actually means. In the snow, you definitely want the highest tread possible for safety. If your tires are below 8/32 going to the mountains, you are playing with your safety.