Near the beginning of the novel, Austen uses detailed imagery to describe Harriet to the readers (note that “a fine bloom” is a reference to Harriet having a rosy complexion):
She was a very pretty girl, and her beauty happened to be of a sort which Emma particularly admired. She was short, plump and fair, with a fine bloom, blue eyes, light hair, regular features, and a look of great sweetness.
Austen intentionally combines literal description of Harriet’s physical form (such as “short, plump and fair”) so that readers can easily picture one of the key characters in the story along with more figurative descriptions, such as that she had “a look of great sweetness,” a description that it is up to readers to fill in for themselves.
It is important for readers to conjure a mental image of Harriet in order to understand why, despite their social class differences, Emma decides to befriend Harriet. This quote makes it clear that Emma is pulled in by Harriet’s “fine bloom” and sweet disposition, and readers become pulled in by these qualities in Harriet as well.
It is also noteworthy that Harriet is described as having “regular features,” whereas—at the very start of the novel—Emma is described as “handsome.” The lack of such direct language about Harriet’s beauty hints that, though she is charming and sweet, she is no match for Emma, something that suitors like Mr. Elton and Knightley also notice.
As Emma is on her way to a Christmas Eve dinner party at the Westons’ near the beginning of the novel, she uses imagery to describe the weather and sky:
The cold, however, was severe; and by the time the second carriage was in motion, a few flakes of snow were finding their way down, and the sky had the appearance of being so overcharged as to want only a milder air to produce a very white world in a very short time.
The “overcharged” sky and threat of a snowstorm not set the scene, such that readers feel like they are in that chilly carriage alongside Emma. But these elements also communicate that just as snow is building up and wants to be released from the sky, something is building up between the characters that will also soon be released.
In this way, the imagery successfully foreshadows the conversation Emma is about to have with Mr. Elton, in which he reveals that his feelings for her have been building over the past few months and that he wants to be with her rather than Harriet (as Emma suspects).
It is important to note that the storm is also what leads all of the characters to leave the party early, putting Emma and Mr. Elton into the close quarters of a carriage together, making it possible for him to propose marriage to her. The cold also allows readers to feel on edge heading into the scene.
Near the end of the novel, Emma is feeling fraught about Knightley possibly having feelings for Harriet rather than for her, and she's also feeling regretful about how she misjudged and mistreated Jane in the past. The narrator uses imagery to describe the setting, which parallels Emma's emotions:
The evening of this day was very long, and melancholy, at Hartfield. The weather added what it could of gloom. A cold stormy rain set in, and nothing of July appeared but in the trees and shrubs, which the wind was despoiling, and the length of the day, which only made such cruel sights the longer visible.
The imagery here effectively mirrors how Emma is feeling on the inside, amplifying her gloomy mood via descriptions of trees and shrubs as “cruel sights.” This is not a winter scene but a summer one—often described in literature as bountiful or lush—and yet, for Emma, the way this summer day stretches on feels too long and “melancholy." Similarly, the wind is “despoiling” nature the way that her feelings and thoughts are despoiling—or harming—Emma herself.
The intensity of Emma's perception of this scene underlines how Emma is finally reckoning with her pride, vanity, and misperceptions (about Knightley, Harriet, and Jane) as well as with her true desire for romantic love and marriage (which she had, for so long, claimed was not the case).