Thanks everybody for the advise. He does sleep on "his" blanket at the end of our bed, so he is inside. I'll try the conditioning you suggest Nanci. It does seem like it could be related to the barometric pressure, as he's started waking up in the night just before a big downpour. This seems to be bothering him more now that he's older, so maybe he's gotten more sensitive to these changes. When he was young he'd just groan a little and go back to sleep.

Now if the Wineter would just end this might not be such an issue!