If your provincial government doesn't require you to change your tires by a certain date, then ideally you want to change your tires when temperatures are consistently hovering around +7°C or lower. Why that number? With summer tires and eventually all-season tires, the grip starts to compromise once temperatures start dropping and the roads become wet. In comparison, winter tires actually gain grip as temperatures decrease, allowing the rubber to stick better on the roads to prevent slipping. So, around the seven-degree mark is when winter tires start to grip better and outperform summer tires and even all-seasons.9
The same applies when you need to change your tires back to summer/all-season tires. Once the temperatures start warming up to +7°C and higher, it's time to change out of winter tires to avoid wearing them out.
Whether the province you live in enforces winter tire laws or not, it's important to know the differences between winter tires and all-seasons. You may be thinking that winter tires are expensive, but when the return on investment is as high as ensuring your safety, it sure does become a wise purchase.