[ColdNoMore]

What "__% chance of rain"...really means.


"Chance of rain" explained.

To be fair, this confusion cannot entirely be blamed on the general public. The terminology most used by people is “There’s a 80 percent chance of rain,” which reasonably leads people to think there’s an 80 percent chance it’s going to rain on them.

And when they don’t see it, they think their local meteorologists are huffing glue.

The factor that’s missing in the comprehension of Probability of Precipitation (PoP)? Area. To quote the National Weather Service (NWS), what PoP is actually describing is the chance of rain at any point over an area.

Here’s the math:

PoP = C x A where “C” = the confidence that precipitation will occur somewhere in the forecast area, and where “A” = the percent of the area that will receive measurable precipitation, if it occurs at all.

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