Well now, I also counted and saw 6 items on that list, however! As Billie said, there were only 5 seasons (one of them was repeated twice!) :)
Well, see you caught something that neither Coby nor I did. That Summer is really in 3 different parts - it starts early, is broken in the middle by a REAL HOT SUMMER, and then resumes plain ole Summer!
You see, Coby and I are Texans, so we didn't catch it - it's just the way it IS here!