If the crescent lies on its back you could hang a bucket on it, and the weather will hold. If it tips, it spills, and rain is coming.

Genuinely old British and Irish weather lore, and a lovely case of a real signal read the wrong way. The crescent's tilt depends on your latitude and the time of year, not on the coming weather, a bucket moon means the Sun's path is meeting your horizon steeply, which in Britain means spring. So it does predict something. Just not rain.