Drivers who live in regions without harsh winters or brutally hot summers may only need one set of tires all year round. For the rest of us, the transition from summer or all-season to winter snow tires will continue to be an annual ritual. Those designed for rainy weather or dry pavement generally don't provide the level of traction needed to plow through thick snow and grip icy roadways. Alternatively, snow tires are designed for cold weather conditions and do not always function well on dry or hot pavement.
Some drivers may be confused by the designation of "all season" tires. While the name may imply equal levels of performance during rain, sleet, mud or snow, the truth is that many are not designed for extreme conditions such as heavy snowfall. There is no real substitute for snow tires when it comes to handling the most brutal winter driving conditions. Snow or winter tires are made from compounds engineered to perform best at colder temperatures, while standard summer types tend to stiffen up as they approach the freezing point.
If you don't plan on remaining home during extreme winter conditions, many experts suggest switching to a complete set of winter tires. Only installing two on the powered wheels would be better than nothing, but the car could also become a bit schizophrenic on the road as certain ones grip and others do not. Some auto shops in snow-prone regions will offer to store a customer's summer tires throughout the winter season, so it may be easier to mount the winter ones on their own rims and allow the mechanics to perform the switch just before the winter weather arrives.
The main concern with different types of seasonal tires is traction and stopping power. There's no law requiring drivers to switch from summer to winter, but there is a noticeable difference between the performance of those tires on snow and ice. Snow tires can be narrow to allow the car to cut through deep, unplowed snow, or they can be wide to maximize the size of the tire patch, the actual area that contacts the road. Summer tires do an admirable job channeling away rainwater, but their treads can become packed with snow and ice and become treacherous. Those designed for the snow have different tread patterns which grip the road and resist snow accumulation.
Individual drivers who live in the fringes of a snow belt are always free to decide whether or not a set of winter tires would be a wise investment, but safety on the road should always be a major consideration. As one car expert explained, a $400 US Dollars (USD) investment in quality snow tires can help a driver avoid paying a $500 (USD) insurance deductible following an accident which could have been prevented.