Panting and drinking a lot of water

I have a white miniature schnauzer who just started panting heavy at night. I put a fan on high directly on her during the night. She is running no fever and just started drinking alot of water during the day.
What could be wrong and what should I do?

NOTE FROM LINDA AND MAX: Drinking excessive water can be a sign that something is wrong, like diabetes. We suggest you get her checked out to be on the safe side.
I did this with Max and it turned out he was fine, he was just drinking a lot of water because he was hot - what a relief!
Good Luck.