I'm not sure on the thickness of the glass, but most windows aren't that thick, so I assumed that it wouldn't hold the weight of the water when full. This is why I was thinking about cutting it- but that no longer seems like a viable option since it's likely tempered. I was afraid of that, but thanks for letting me know so I didn't end up sweeping the garage. Is window glass also tempered?

NOOoooo...Potts, say it ain't so!!!