We often glance at the percentage of rainfall for our location, but what does this number actually mean?

Some people think that if you see 60% next to expected precipitation in the forecast then you have a 60% chance of rainfall. This is actually not the case.

Nor is it the case that rain will fall in 60% of your area. In fact this percentage is more complicated than you might think.

The percentage is based on something called the Probability of Precipitation (POP). But what makes POP confusing is that there are five commonly used definitions used by meteorologists.

Most commonly, POP is the likelihood that an area will get some measurable rainfall in a particular timeframe. This calculation is based on the confidence level that rain will develop and how widespread it is likely to be taking into consideration showers or rainfall.

At Weather & Radar, we calculate this value using an algorithm with different parameters like convective conditions and evaporation conditions. This algorithm then gives us an idea of how likely it is for precipitation to happen.

However, seeing the percentage is often not enough to know whether it will rain. Therefore, when the POP value is greater than 50%, it is best look at our Weather Map or 90 Minute Forecast to see what type of rain you can expect.