I am most concerned not that a child can and will wake up in an ugly mood; I'm concerned you say this has been happening for "the last few months". That's too long not to be concerned and clearly you are. Let me ask you some questions to ask yourself, Maybe they will trigger a thoughtful exploration and some productive discussions that will address this situation.

Has your son always been sort of grumpy when he gets up and can this most recent morning ugliness be considered a more exaggerated example of an already existing behavior pattern?

If you step back and take a look at what was happening in your son's life prior to and possibly continuing through this recent ugly mood period, were and are there any upsetting events in his school life, social life, family life, extra-curricula life that could be creating emotional problems he won't or can't share with you?

Does this waking up and morning ugliness manifest itself every day, vacations? Has he had disturbed sleep and/or nightmares he has awakened from? Have his teachers or any other people who see him on a regular basis noticed a change in his moods and/or behavior? Other than his morning unhappiness, does he seem to be enjoying his life, seem to be behaving like his "usual self"?

You may want to find some quiet, relaxed time when the two of you can be alone and express your concern that he hasn't seemed happy at all for a long time when he starts the day. You can say that it can't be much fun for him to look forward to getting up each day so miserable and that you were wondering if there was something he'd like to tell you about that could help you understand why this has been happening. Don't blame him for the moods, just non-judgmentally empathize with him and see if it leads anywhere.

If you find him to be sad all the time, withdrawing from everyone, unable to enjoy himself on a continuing basis, you might consider seeing a child/family therapist to talk about this further. I wish you and your son well.