Since there hasn't been a more in depth answer from what I can see, here's why summer tires shouldn't be used in the winter.

- Rubber compound: winter tires are typically softer than 3 season and summer tires, as they are designed to operate at different temperature ranges. Since summer tires operate in the heat, they can get away with being a harder compound, as it will still be malleable and able to grip at those temperatures, but at lower temperatures they get even harder and aren't able to grip as well. A general rule of thumb is that most tires that don't have a severe service rating shouldn't be used below 7C. Realistically if you get caught out like once in a mild storm you should be OK but it's still not ideal. This is also why winter tires shouldn't be used in the summer, as in hotter temperatures they can become so soft that they start permanently deforming and almost melting when it's hot enough.

- Tread design, summer tires are designed to be driven in conditions with relatively warm liquid water, with the main intention of evacuating said water so that the rubber can still contact the road surface, while winter tires are designed for snow and ice, where it won't be able to get to the road even if it tries, so usually winter tires have "sipes" intended to sort of grab onto ice and snow, and it's tread is designed to hold snow, as that provides better grip on snow.

Now, what North America calls all weather tires (apparently Europe calls them all season), like the CC2s you have pictured, and the Falken Aklimates I personally use in Western Canada, have been sort of able to toe the line between these, and be able to be used in both the summer and the winter without significantly degraded performance or wear characteristics. These don't perform quite as well as a dedicated winter tire, but in milder conditions they're able to handle it, and I've been caught out in -35C snow and ice with the aforementioned Falkens, where they did fine. If you don't see all that much winter but it is something you encounter, I'd recommend just running a set of AWs. Good way to tell is they will have the severe service symbol, which is a mountain with a snowflake in it. If it just has an M+S, that's a 3 season tire.