Imagery is a literary and stylistic technique employed by an author to help a reader create a mental image of the text at hand. Well constructed imagery appeals to the senses (sight, touch, taste, sound, smell) of the reader. The more appealing to the senses, the more depth the image the reader creates in his or her mind. In regards to James Hurst's "The Scarlet Ibis," the text contains numerous references to the weather. Within these references, imagery enhances the mental picture the reader constructs.
Summer was dead, but autumn had not yet been born.
Here, the image of the weather is very specific. Although Hurst compares both summer and autumn to human life (a traditional comparison), he does so in a very novel way. Summer, dead, illustrates a complete lack of possessing any of the five senses. Autumn, on the other hand, is on the verge of being born (with "its" senses new and peaked).
The "bleeding tree's" imagery appeals to the sense of sight of the reader. A tree bleeding provides the reader with a very distinct visual image. While not weather imagery, it illustrates the power of Hurst's language and stylistic choices.
Thunder was drowning out the sound of the sea.
Here, the imagery appeals to the reader's sense of sound. Unfortunately, Hurst's image alienates any reader unfamiliar with the sound of the sea. Fortunately, most people are very familiar with how thunder sounds.
The rain came, roaring through the pines.
Here, Hurst's language is metaphorical. The rain roars like a lion. Both appealing to the sense of sound and sight for the reader, Hurst doubles the image appeal.