Random Thought #9

So we've had a bit of rain recently as TS Hermine just rolled through and every morning, I hear on the radio what our percentage of rain is going to be for the day. It's always something like 20% or 60% or whatever. I thought to myself, how can you have numbers like that? My thinking would be you have 3 choices. 0%, 50%, 100%. Either it will rain for sure, there will be no rain whatsoever, or you have a 50/50 shot of one or the other. How do they measure this stuff? I think we should all hold meteorologists more accountable :P