The correct answer to this open question is the following.
Unfortunately, you forgot to include the name of the story or the name of the book.
How do we know what are you talking about?
We had to do some deep research in order to help you and can comment on the following.
In the description of the setting in lines 24-26, what the special wind suggests about the locations of the two armies is that the sound of the wind -or at least is why the boy thinks it is- is, in reality, the sound of the armies that are marching and getting closer. The fact that the boy can hear the sounds so close means the armies' camps are very close to each other.
And regarding the mood, the above-mentioned descriptions help to create a mood of tension, even anxiety for the things that are about to happen in the story.
We are talking about the story of "The Drummer Boy of Shiloh." The story of John Lincoln Clem (1851-1937), who was the drummer boy during the American Civil War for the Union Army.