What is the atmosphere in the story "A Days Wait"?

The atmosphere of Ernest Hemingway's story "A Day's Wait" is somber and negative.
There is nothing cheerful about this "slice of life" story; it begins negatively and ends somberly. In fact, the negative atmosphere serves to amplify the seriousness of the effects upon Schatz's psyche as he lies alone in his room, believing that he is going to die. For, when the doctor visits, Schatz overhears him tell his father that his temperature is one hundred and two, but Schatz believes the doctor expresses this temperature in Celsius. After hearing the doctor, Schatz's

... face was very white and there were dark areas under his eyes. He lay still in the bed and seemed very detached from what was going on.

The boy is reticent about his condition and his feelings, so the father does not recognize Schatz's fear that he is going to die. Simply assuming that his son might wish to be alone, the father leaves for a while. But, when he returns, he finds that the boy's face is blanched with only the tops of his cheeks are flushed as he still has a fever. "...the boy had refused to let any one come into the room." He even refuses his father entry, warning his parent, "You mustn't get what I have."
Finally, the father learns that Schatz has mistakenly believed his temperature to be measured in Celsius since he has gone to school in France. Stunned, the father remarks, "He had been waiting to die all day, ever since nine o'clock in the morning." Further, the father is virtually speechless as he thinks of Schatz alone for hours in his anxiety. All he can say is "You poor Schatz" as he realizes the somber psychological repercussions upon his son who thereafter "cries easily at little things of no importance."