How Meteorologists Estimate the Chance of Rain or Snow

Social media videos are a fantastic escape! If my husband wants to watch football but I still want to spend time with him, I hop on Instagram or scroll through Facebook Reels. (TikTok is kind of weird, though.) The algorithm has done a great job curating my feed, showing me videos about food, horses, and all sorts of things I didn’t even know I was interested in. (Too good if you ask me...)

Today’s lesson was about Weather.

Back in 2008, when I was getting married, I watched the weather like a hawk. On the big day, I was heartbroken when the forecast came in: 100% chance of rain, and we were planning an outdoor ceremony. I decided to go through with it anyway and take my chances. It turned out to be sunny and 75 degrees for our photos. But when it started thundering during the ceremony, I prayed hard! Thankfully, the rain held off until we were all inside the Old National Events Plaza, sipping champagne and enjoying a huge fruit display.

TikToker Says 30% Chance of Rain Isn't What We All Thought

So, back to the video I saw. Sidneyraz is a content creator who uses the "I was today-years-old when I found out something" schtick for his videos. In this video, he said that he had it all wrong. A percentage of rain means that a percentage of the area might get rain. So, it would be like saying 30% of the tri-state will get rain.

I thought, whaaaa? I am today-years-old too! But, here's a secret about the internet - you should NEVER believe ANYTHING without verifying it with a RELIABLE source.

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Was He Right?

So first, I checked the comments.
There were a lot of folks who didn't agree with this defintion like Johnny and Angelo.

Johnny Dingledine: Dude.... just stop..... this isn't even accurate

Angelo Fiouris: How much more wrong could this guy be.

Jeffrey tried to clear things up a bit.

Jeffrey Mickel: No. It means that 30% of the time that the same weather conditions happened, it rained. Meaning out of 100 times that those specific temps, barometric pressure, cloud cover, etc. happened, 30 of those times it rained."

Some denounced meteorologists as charlatans handing out #fakenews.

Lisa Henson Thomas: They’re are not psychic. Always thought it was odd the news makes a forecast. Where is the crystal ball & fortune teller.

And there were those who just would rather do taxes or really anything else than talk weather, like Lee.

Lee Kehlet: After scrolling for a bit and reading comments and replies I truly couldn’t care less about which one is right. I’m genuinely more concerned with the lack of reading comprehension going on. People arguing with each other and saying the same thing, people posting 3rd party search results and research that they’re not understanding….the level of intelligence on display here could be described using fractions

What is "Probability of Precipitation"?

I always think it's best to go to the experts. For me, that's the National Weather Service. Here's what they had to say.

Forecasts issued by the National Weather Service routinely include a "PoP" (probability of precipitation) statement, which is often expressed as the "chance of rain" or "chance of precipitation."

EXAMPLE

THIS AFTERNOON...MOSTLY CLOUDY WITH A 40 PERCENT CHANCE OF
SHOWERS AND THUNDERSTORMS.

The "Probability of Precipitation" (PoP) simply describes the probability that the forecast grid/point in question will receive at least 0.01" of rain. So, in this example, there is a 40 percent probability for at least 0.01" of rain at the specific forecast point of interest!"

This means there’s a 40 percent chance that rain will occur at some point in the forecast area. It doesn’t mean it will rain for 40 percent of the time or cover 40 percent of the area; rather, it indicates that out of many similar days, rain would be expected on 40 percent of them. So if you're in the area, there's a good chance you might want to keep an umbrella handy!

A Meteorologist Breaks it Down

Hmmm well, what do actual meteorologists have to say? Holt Hanley, meteorologist with a Master’s in Meteorology, said that it's a little more complicated. He said that the probability for precipitation that meteorologists use is the "percent area that we're going to see rain, times forecaster confidence." He breaks it down in a video.

At this point, I'm going to go with Lee and just not think about this anymore because it's making my brain hurt!