Up here in the frozen ass-end-of-nowhere, there's no such thing as an all-season tire. In higher elevations where snow and ice can be expected we regularly see vehicles upside-down in straight, flat stretches of road. Pull over to help and invariably, all four-feet-to-the sky are more than half-worn all-season tires.
Two things I've learned:
1. Brand-name winter tires (Nokian and Glslaved are my current choices) mounted and balanced on their own wheels are worth the cost and the hassle. Example, a trip is planned and there's an early snow. The tire stores are slammed and can't get you in before you have to leave, Yes, it's a minor hassle to switch over yourself, but you can leave on schedule and travel safely.
2. When winter tires are worn below half the original tread depth, begin the search for new ones. If one should run them down to the legal 3/32" wear bars, that's an accident looking for a place to happen.
2017 Bolt Premier Cajun Red
2011 Saab 9-4X
2005 Saab 9-5
1998 Saab 9000 Aero
2004 Ford F250 6.0 Turbo Diesel
1963 Studebaker Avanti
1956 Studebaker Hawk custom with a supercharged Packard V8
1955 Studebaker custom pickup with a Packard V8