As a general rule, when you’re using the name of a season in a sentence as a noun or an adjective, it shouldn’t be capitalized. There are only a few times when seasons should be capitalized, including when they’re used as proper nouns, when they start a sentence, when they’re used in titles, or when they’re personified.
Seasons as Nouns or Adjectives
When a season is used in a sentence as a noun or an adjective, it should begin with a lowercase letter. The same rule applies to the words springtime, summertime, and wintertime when they’re used as nouns in a sentence.
For example, consider this line from Charlotte’s Web by E. B. White: “The barn was pleasantly warm in winter when the animals spent most of their time indoors, and it was pleasantly cool in the summer when the big doors stood wide open to the breeze.” In this case, the seasons winter and summer are not capitalized because they’re used as nouns.
Seasons as Proper Nouns
A season should be capitalized when it’s being used as part of a proper noun (a noun that describes a particular person, place, or thing) as in Winter Olympics.
Seasons at the Beginning of a Sentence
As with normal sentence capitalization rules, the name of a season should be capitalized when it comes at the beginning of a sentence, such as “Winter is my favorite season.”
Seasons Used as Titles
When a season is used in a title, it should be capitalized. Some examples of this rule include the books Silent Spring by Rachel Carson, Freedom Summer by Doug McAdam, Drums of Autumn by Diana Gabaldon, and Brian’s Winter by Gary Paulsen.
In poetry and other literature, personification is giving an animal, inanimate object, or abstract notion the qualities and attributes of a human. When a season is used this way, it should be capitalized.
Take, for example, this passage from “Summer,” a poem by Charles Mair:
We will muse on Summer‘s ploys:
How no partial gifts are hers,
But now the palms and now the firs
Are dozed with kisses balmy-sweet
From lips which breathe a pulsing heat.
In this poem, summer is capitalized because the season is being discussed as though it’s a person whose name is Summer.