What rain chances actually mean

By Josh Linker, Meteorologist
Last Updated: Wednesday, July 08, 2015, 4:51 PM EDT

Now that we are a month into our rainy season, let’s reexamine the rain chances. People often ask us what does the percent chance of rain actually mean.

For this purpose of this blog, we will discuss our summer pattern, or at least weather similar to the summer pattern. Let’s be honest here, just about every day, there will be thunderstorms somewhere in Central Florida between June and September. The big question is where will they be and how many will there be?

This is where our percent chance comes in. It is also where certain wording comes in. For the purposes of our summer weather, the chance for rain and the coverage of rainfall is essentially the same thing.

Since we know that there will be rain somewhere and we say a 50% chance for rain, that means that half of the area will see rainfall that day. Now, with that said, we try to do a good job in communicating where we think the best chances will be. Perhaps we would say a 50% chance today but favored spots are inland so maybe 20% or less near the coast, but 70% or higher inland, again, as an example.

But, if you think about it, it really means the same thing. Let’s say there was a 50% chance for rain but we weren’t certain where a favored spot would be. So, if we say half the area would receive rain and you are in a random location, you have a 50/50 shot of getting rain that day. Make sense?

Now with respect to some of the words we use. Again, this is under the premise that rain is going to fall somewhere. We might use isolated interchangeably with a 20% chance, or scattered for 30%-50%, widespread or numerous for higher than that.

It is important to remember that rain chances have nothing to do with the intensity of the rainfall, the duration of the rain or the time of day. There could easily be a 20% chance in the summertime and someone could still get 3 inches of rain. It would simply be that 80% of the area wouldn’t get any.

Hope this helps for the rest of the summer rainy season.