I had the Hue indoor sensor mounted outside the front door for over a year, through all weathers and it was fine - but it was tucked up into a nook that shielded it from the rain.
It's only IP42 vs the proper outdoors one which is IP54 - so any water damage failures are at your own risk and you'd have no comeback on the warranty.
I've had mine also outside but tucked away under an overhang for 2 years now with no issues. In reality it's probably a better environment than the one in my bathroom has.