In the Summer time,Earth is a few million miles further away form the
Sun and the Northern Latitudes are tilted toward the Sun.In the Winter
time,the opposite is true.That is why we have Winter,Spring,Summer and
Fall.Maybe all of that has something (along with the Sunspots too) to do
with radio reception.Well,of course it does.

The earth is closest to the sun (perihelion) in early January which is
summer in the southern hemisphere. Six months later in July we are
farthest from the sun (aphelion) which is summer in the north. This is
why shortwave conditions are generally poorer at this time of year in
the northern hemisphere because we are farthest from the sun and
therefore receive less radiation to energize the ionosphere. The longer
days of summer in the north help to compensate for this effect to a
certain degree but not completely.