Is it cold in Germany in early September? We are going to Berlin, Germany at the end of this month, and it is still very hot. ...

It's very cold in Germany this summer. It's cool in the morning and evening and hot in the afternoon (it's 13-25 degrees now). I suggest you take at least one sweater and one jacket. If you are a girl, it is safer to take an umbrella. Two pairs of shoes are ok, and slippers must be brought, because hotels in Germany are not equipped with disposable slippers for environmental reasons.