The Chicago Style Manual holds that the four seasons an their derivatives should be lowercased. In other words, spring, summer, fall, winter, and the words formed from them, like springtime and summertime, should never appear capitalized in your text. For example,
- My brother’s birthday is on the winter solstice.
- Michigan winters are very cold.
- Looks as if springtime is finally upon us.
The one exception to this rule is when the season is used to denote the issue of a journal. For instance, some journals do not run on a monthly runtime but a seasonal one. In this case, when the season is standing in lieu of a month, it should be capitalized. For example,
- The Fall issue of Great Reading Magazine was better than usual.