One of the most misunderstood terms used by weather forecasters is the "Probability Of Precipitation," or POP. The National Weather Service includes POPs in their one and two-day forecasts whenever there's a mention of rain or snow.

The probability of precipitation is best explained by example. Let's say the forecast calls for a 60% probability of rain tonight in your county. This means that there's a six-in-ten chance that any location in your county - your house, for example - will receive at least 1/100th of an inch of rain by morning. Looked at another way, if we consider a set of ten accurate forecasts that call for a 60% probability of rain for your county, it would rain at least 1/100th of an inch on your house six of the ten times. Therefore, a 60% probability of rain does not mean that it will be raining 60% of the time - or that at any given time rain will be falling on 60% of the county. Nor does the probability of precipitation imply anything about the intensity of the rain.

The National Weather Service and other forecasters also sometimes express these numerical probabilities in words, such as "isolated," "scattered," and "numerous." As one example, a 40% probability of precipitation during the summer could also be expressed as "scattered" thunderstorms.