In To Kill a Mockingbird, to what time and place does Scout compare the courthouse atmosphere before the jury returns?

Scout employs an extended metaphor to compare this tension-filled scene in the courtroom to the morning Tim Johnson, the rabid dog, threatened the streets of Maycomb. Let's examine this quote in segments.

The feeling grew until the atmosphere in the courtroom was exactly the same as a cold February morning, when the mockingbirds were still.

In the same chapter that describes the scene with Tim Johnson, Scout explains that Miss Maudie has taught her that it's a sin to kill mockingbirds, because their sole purpose is to create beautiful music for humans to enjoy. In the novel, mockingbirds become symbolic of innocence. Here, Scout calls to memory those silent mockingbirds as Tom Robinson, who is a symbolic mockingbird himself, awaits his verdict. While the courtroom seems to hold its collective breath, all sense of innocence hangs "still" in the balance.

A deserted, waiting, empty street, and the courtroom was packed with people.

Scout compares the similarities of the waiting street on that cold February morning and the sense of anticipation in the courtroom. Tim Johnson's disease is rabies, a deadly virus that is not compatible with life. Rabies attacks the central nervous system of all those it infects and slowly destroys their ability to think and live. The courtroom faces the disease of racism, which is also a deadly contagion. It also destroys all those it infects, replacing compassion with hatred and rational thought with blind ignorance.

Atticus had stopped his tranquil journey and had put his foot onto the bottom rung of a chair.

Atticus is central to both Tim Johnson's story and Tom Robinson's. The sheriff himself trusted Atticus to take the shot and kill Tim Johnson, sparing the neighborhood the possibility of being bitten and therefore becoming infected as well. At the trial, the judge trusts Atticus to give Tom Robinson the most fair trial possible, which is a step toward progress, even if the outcome demonstrates the grip of racism over Maycomb. Although Atticus is able to quickly end the threat of rabies on the streets of Maycomb, he is unable to save Tom Robinson from the disease of racism.

Scout is waiting for the jury to come out with the verdict in chapter 21.  Moments before the jury comes in, Scout tells her readers that the atmosphere in the courtroom reminds her of a cold February morning from a previous year.  

The feeling grew until the atmosphere in the courtroom was exactly the same as a cold February morning, when the mockingbirds were still, and the carpenters had stopped hammering on Miss Maudie’s new house, and every wood door in the neighborhood was shut as tight as the doors of the Radley Place.

Scout does not go into any further detail than that, but it is enough detail to remind readers of events that take place in chapter 10.  Jem and Scout are out playing with their air rifles, and Jem sees a dog acting weird in the distance.  The dog is Tim Johnson, and just the sight of his odd behavior is enough to spook Jem into going home to tell Calpurnia.  

“Cal,” said Jem, “can you come down the sidewalk a minute?”

“What for, Jem? I can’t come down the sidewalk every time you want me.”

“There's somethin' wrong with an old dog down yonder.”

Calpurnia immediately recognizes that Tim Johnson is a mad dog and is a major threat to everybody in the neighborhood.  She immediately begins making phone calls to ensure that everybody stays inside.  She also makes a call to Atticus.  Atticus and Heck Tate show up, confirm that the dog is mad, and Atticus shoots the dog dead with a single shot.

Before Atticus shoots the dog, Scout takes a moment to tell her readers what the entire atmosphere of the neighborhood felt like.  

Nothing is more deadly than a deserted, waiting street. The trees were still, the mockingbirds were silent, the carpenters at Miss Maudie’s house had vanished.

The dog’s presence brought an ominous and foreboding feeling.  Scout knows that things aren’t right.  It feels as if something deadlier is going to happen, which is what happens.  She gets that same feeling at the courthouse.  She knows that something isn’t quite right, and she is reminded of the awful conclusion to the Tim Johnson event.  The reminder serves as a way to foreshadow the jury’s negative verdict.  Scout feels as if something bad is going to happen, and those feelings are soon confirmed.

In To Kill a Mockingbird, what does Scout compare the courtroom atmosphere to?

Scout compares the atmosphere within the courtroom to the impression she once felt the winter before.

One February morning, for whatever reason, Scout experienced an ominous silence outdoors:

...the mockingbirds were still, and the carpenters had stopped hammering on Miss Maudie's new house, and every wood door in the neighborhood was shut as tight[ly] as the door of the Radley house. A deserted, waiting, empty street....

Now, the courtroom has this same feeling of a suspension of time. It is as though all the people in the courtroom are collectively holding their breath, not daring to think of what they will soon hear from the foreman of the jury. Scout and Jem and others know that the innocent "mockingbird" Tom Robinson, too, has stopped any "singing," for he is all too aware that his life hangs in the balance. In one sense, Mayella's untrue accusations, Bob Ewell's overt racism, and the oppressive of Jim Crow regime are all "doors" that are shut "tightly" against Tom.

Little Scout would not be familiar with Shakespeare's Hamlet, but the troubled young Dane comments in a similar fashion upon the state of things after he has been visited by his murdered father's ghost: "This time is out of joint." The eerie silence in the courtroom and the wicked injustice of Tom's trial serve to make Scout feel as though "time is out of joint."