People living in countries or regions up north will have snow earlier than those living in the southern parts. However, the northern regions tend to be better prepared as they expect snow to come early and they will always have solid winters. So they know that winter tyres are mandatory and will thus change to winter tyres much earlier. People living in the southern parts might not see that much snow and are more likely to be taken by surprise by snowfalls.
As summer tyres are not able to manage during winter conditions, you will need to change to proper winter tyres, if you are expecting snow and winter conditions. You don’t actually have to have snow, it is enough with minus degrees for winter tyres to outperform summer tyres. This is due to the rubber compound used in summer tyres. It is different than that used in winter tyres. The rubber compound is optimised with different additives to be soft and agile during winter conditions. It allows them to comply to the surface and to have enough friction to work properly.
In addition, winter tyres are designed to have great traction despite slippery surfaces. This can be done though the tread design and even with the addition of studs into the tread. With proper metallic or ceramic studs, you will have the best properties for managing your car on icy surfaces. So if you are expecting a lot of icy surfaces in the area where you live, these studded tyres are the best winter tyres for these types of circumstances.
So not only are you dependent on having great winter tyres, you are also dependent on having them mounted before the winter arrives. If you are late with switching tyres, you should not attempt to drive your vehicle. It would be very much as trying to leave the house with summer shoes. It is clearly a bad idea. So you are best to leave the car and wait at least until snow or icy conditions have passed. Failure to do so can both be illegal and it will for sure jeopardise your safety and the safety of others.