Why are the seasons of the year (winter, spring, summer, autumn) not capitalized?
It's true that things change. Many people remember (or think they do, as you say with your "almost certain") being taught to capitalize the seasons. I didn't look for historical style guides to see if there was a time 30, 60, or 100 years ago that recommended capitalizing, but certainly you don't do it now.

Here's a quick link to the Online Writing Lab at Purdue: http://owl.english.purdue.edu/owl/resource/592/01 /
AnonymousWhy are the seasons of the year (winter, spring, summer, autumn) not capitalized?
Capitalisation tips

  • If a title comes BEFORE a name, capitalise it. (Mayor Joe Smith was on television.)
  • If a title comes AFTER a name, don't capitalise it. (Joe Smith, mayor, was on television.)
  • All national titles are capitalised no matter when/how used. (George W. Bush, President.)
  • Capitalise family relationships when used as a name (Mother) but not as a description (my mother).
  • Capitalise geographic locations (the South) but not directions (south of the border).
  • Capitalise months, days, holidays (June, Monday, Christmas) but not seasons (summer, winter

Students: We have free audio pronunciation exercises.
I am confused. I am almost certain that I was taught in school that the seasons were always to be capitalized. However, I am now finding that it is not the case. When did this change? I have asked others my age who say the same thing. It seems the rules of grammar are changing and the commentary I find makes it sound like it has always been that way. Was I taught incorrectly or has it changed?
 BarbaraPA's reply was promoted to an answer.