Except that it doesn’t. At least not the way I have the weather set. January should automatically come with snow in my latitude.
Update:
If I set the “snow” slider to a non–zero value, (like 17 cm), there is still no snow.
I could even accept the green trees as there are a lot of conifers at this latitude, (though there are a lot of other trees too), but the absence of snow is obviously jarring.