Indeed: 1. any percentage prediction like "99,999999999999%" chance of rain is still 100% correct if it doesn't rain. 2. its my understanding (from a trip to

Indeed: 1. any percentage prediction like "99,999999999999%" chance of rain is still 100% correct if it doesn't rain. 2. its my understanding (from a trip to the local weather bureau) that an "80% change of rain" means something like "when conditions in the past were like they are now, it rained 4 out of 5 times". Happy to be educated otherwise.