If A seems to be B now, then use the present simple. If A seemed to be B in the past, then use the past simple. "I have just looked out of the window. It seems to be raining now. It seems that the rain is heavy. It seems that the rain will continue for a long time because the clouds are so black." "I looked out of the window earlier today. It seemed to be raining. But it seemed to stop about an hour ago." "I used to like my neighbour. He always seemed to be such a nice guy. But it seems that he hit (past) his dog yesterday and so he doesn't seem so nice now." The tense of "seem" can be different from the tense of the second verb. It depends on your meaning. I recommend that you practice with other sentences.