[2BNTV]

According to Google:

Using a 50% probability of rain as an example, it does not mean (1) that 50% of the area will be covered by precipitation at given time in the given forecast area or (2) that you will be seeing precipitation 50% of the time in the given forecast area for the given forecast time period.

Let's look at an example of what the probability does mean. If a forecast for a given county says that there is a 50% chance of rain this afternoon, then there is a 50% chance of rain at any point in the county from noon to 6 p.m. local time.

Now , back to my discussion of how many angels dance on the head of a pin.