There are no true
"seasons" on Jupiter. The lack of seasons is a result of Jupiter's axis of
rotation being almost
perpendicular to its
orbital plane. The
tilt is only 3 degrees which is less than the tilt of any other
planet in our
Solar System. What that means is that Jupiter rotates around an
axis that is
practically perfectly vertical relative to its
orbit, consequently no part of Jupiter gets more direct sunlight at some time of the year than at any other time of the year. If no part is closer to the sun at any one time of year than another time of year then the
climate doesn't vary according to the
time of year and thus you don't get
seasons.
Thanks to hobyrne for a minor correction.