Belgium is likely to be damp and overcast, and cool but not particularly cold. If you consider hiking, bring some water-resistant clothing. Even if it doesn't rain, from October to about May-June, the ground never dries out. Your shoes will get soaked just from walking through the grass.
At low altitudes, Switzerland will have similar weather, possibly slightly warmer. But hiking in the high Alps is not feasible during November. It's the shoulder period between the summer hiking and winter skiing seasons. Not enough snow yet for skiing, but too snowy, damp and cloudy for enjoyable hiking.