The first two lines of "Acquainted with the Night" establish the setting, uses vivid imagery to illustrate the speaker's emotional mood. In the first line, the speaker declares that they are "acquainted," or familiar, "with the night." On a physical level, the speaker is familiar with the night as the speaker is taking a walk through the city during the nighttime. However, the night brings darkness, which is often associated with negative feelings such as despair, sorrow, or isolation. Therefore, "night" can also be a metaphor for these particular emotions. Thus, the speaker's declaration of familiarity with the "night" suggests a familiarity with despair, sorrow, or isolation as well.
The term "acquainted," which suggests connection, is used in an ironic manner here to describe the speaker's connection to isolation—or, in other words, the speaker's very lack of connection. Thus, the speaker is not connected to any other humans, the way one might be "acquainted with" friends or neighbors. Rather, the speaker is connected to sorrow, despair, and isolation.
In the second line, the speaker states that they have begun and ended a walk in the rain. The use of epistrophe in the repetition of the phrase "in rain" emphasizes the fact that the rain is unceasing and relentless. The rain is often associated with sorrow, as raindrops are often metaphorically compared to human tears: the speaker's sorrow, like the rain, is unceasing and steady. Neither the rain nor the speaker's sorrow abate during the speaker's walk.
"Acquainted with the Night" is a terza rima sonnet with the traditional 14 lines and ending couplet. Each line is also written using iambic pentameter, which is typical for sonnets. As with any sonnet, the opening of "Acquainted with the Night" establishes the "problem" of the poem—in this case, the speaker's sense of despair, sorrow, and isolation. However, the unconventional use of a terza rima rhyme scheme sets the reader up for similarly unconventional takes on the traditional sonnet form, hinting that this problem may not end up being solved.