Answer:
It suggests a coming storm.
Step-by-step explanation:
Syntax is the study of rules governing the construction of sentences in natural languages. Syntax is the part of grammar that studies the arrangement of words in phrase and sentences in speech, including their logical relationship, among the multiple combinations possible to convey a complete and understandable meaning. In this case, the author's syntax in this passage, through the excerpt "During the whole of a dull, dark, and soundless day in the autumn of the year, when the clouds hung oppressively low in the heavens ..." indicates that a storm approaching.