Bad weather in northern Europe means that everything is covered in snow for a long time. I think that's slightly more than just reduced output. The snow also tends to cover am area that's hundreds of kilometers in every direction too.
I've lived in Sweden and Finland. It's actually the lack of sunlight that is causing issues with solar. The snow is much less of a concern. E.g. Helsinki only gets a few hours of daylight and the sun does not get much above the horizon in the winter months. The reverse is true as well; you get insane amounts of sunlight in the summer months. Luckily there's wind, hydro, wood pellets, and a few other alternatives.
Further south in Germany, Netherlands, etc. Solar is usable throughout the year and quite common. Obviously output in the summer is going to be much better than during the winter.
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