"I am reading for an hour."
Translation:Jeg leser i en time.
It might depend on context, but the way I read it at least, it could be expressing immediate intention (= I am going to read for an hour) or stating how long I am going to continue something I have started (= I am in the middle of an hour's reading time). There could also be an implied "so don't bother me until I'm done." Whatever the case, the emphasis seems to be mainly on the duration of the time, so the point in time that is happening/going to happen is less important, or clear from the context.