Understanding the math behind your daily rain chance
ROANOKE, Va. – Ever looked at the rain chance for tomorrow and wondered, “What does a 30 percent chance of rain actually mean?” You’re not alone. 10 News’s meteorologist Delaney Willis has the answer, and it’s a little more involved than just flipping a coin.
During a recent Weather Authority broadcast, Delaney Willis explained that the percentage you see in the forecast—officially called the Probability of Precipitation, or POP—is calculated by multiplying two things: how confident the meteorologist is that precipitation will happen, and how much of the local viewing area is likely to see it. In Delaney’s words, “Take the confidence and we multiply that times the area and that equals that percentage.”
This formula means the number reflects both the certainty rain will fall somewhere and how widespread it’s expected to be. For example, a “50 percent” chance might mean a high certainty that only half of the area will see precipitation, or moderate certainty that the whole area could get wet. The next time you check the rain chance, remember: it’s not just about a coin toss—it’s about the odds and the coverage.
What’s in the forecast? Mostly low rain chances ahead
According to the latest forecast, a 30 percent chance of rain is expected today. After that, periods of dry weather are likely over the weekend, and as the workweek returns, rain chances drop even lower, with numbers in the 10 to 20 percent range showing up on the Weather Authority charts.
Delaney Willis shared that, unfortunately, as these next few days arrive, rain probabilities remain on the low side. That means while an umbrella might not be totally necessary, it might still be a good idea to keep an eye on those percentages, especially for outdoor plans.
Recent dry stretch and what it looks like outside
It hasn’t just felt dry—it looks that way, too. Delaney pointed out on-air that it’s “starting to affect what we’re looking at outside in terms of brown of the grass and some of the trees you might notice out and about.” The local area has seen several dry days in a row, and it’s becoming pretty obvious just by glancing at lawns and parks.
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Bottom line: What to watch for
Understanding rain chances helps take a little guesswork out of your plans. Keep in mind that low numbers mean both the expectation of rain and how much of our area will likely be affected are on the lower side. Stay updated with 10 News and WSLS.com for the latest details as those numbers change day to day.