Any reader of literature, especially poetry, soon becomes aware of the importance of the seasons of the year in expressions of human experience. The seasons may be the four of the moderate zones or the two or three seasons of tropic zones. For instance, in Indian poetry, the rainy (monsoon) season is the time of love affairs since the heavy rains rule out most other activities. A contemporary poem expresses the traditional theme well.
I began writing this entry on August 2. which is close to the beginning of autumn in some traditional schemes of the seasons. Typically, I’m returning to it on August 9. The temperatures have cooled down, and there’s a scent of autumn in the air. (For my nose at any rate.)
So, has autumn begun? That depends on where you live and whose definitions of the seasons you use. In Japan’s tradition, it is indeed autumn now. The "season word" (kigo) is an important part of the traditional haiku.
An article on Wikipedia discusses various scientific and cultural aspects of the seasons across the world. Of especial interest to lovers of literature is the discussion of traditional seasons. Perhaps you have wondered why, if the solstice in June is the beginning of summer, midsummer’s eve is a little earlier in June, the middle of the season illogically preceding its beginning.
Contemporary climate changes are affecting the literary seasons, as discussed in an article in The Telegraph. At the end of the article, a list of natural phenomena associated with spring shows a common poetic interest with Japanese culture.
The point finally is that the boundaries of the seasons — when they begin and end — are human constructs, depending on climate and culture.
For a well-known interweaving of season and human life, read Shakespeare’s "That time of year thou mayest in me behold."