10%

A 10% chance of rain means a 90% chance of not raining, right?
Wrong

Seems it means "there-is-a-definite-possibility-of-rain-but-are-only-going-to-a-call-it-a-10% -chance" because it did rain that night.
The night we got 4 round bales of hay for the winter and didn't have the place ready to put them.
Yeah, that would be the night.
So much for thinking optimistically!

Thankfully it was only a light drizzle and it didn't affect the hay.