The Question and Answer section for Number the Stars is a great resource to ask questions, find answers, and discuss the novel.
At the end of the novel, the Uncle Henrik delivers the Rosens (including Ellen) and the other refugees to Sweden. The packet that Annemarie delivered to her uncle contained a handkerchief soaked in a chemical that eliminated the soldiers' dogs'...
It does not really said in chapter five. It is raining a lot and it gets dark early. It could be late fall or winter.
Ellen begins to understand just how brave her parents are. Ellen is also more aware of the fact that her parents could be in mortal danger. When she goes to sleep, she is not worried about her own safety, but that of her family.