sunspots? riiiight.... someone was selling you something
Trees, absolutely. If you can't get clear LoS, don't bother. Trees will also make rainfade much worse, since when it rains the leaves get wet and further block the signal.
However, a properly mounted/aimed dish simply will not "fade" these days, except during extreme weather. Chances are, cable will be out as well in those situations (at least if you live around here, or chicago)