SAN ANTONIO — Here at KENS 5 our team of meteorologist do their best to make sure every weather forecast is as easy to understand as possible. In tonight's Verify we look into one aspect of a weather forecast that may have some in South Texas scratching their heads at times.
THE QUESTION
Is it true that a 30 percent chance of rain means anybody in the forecast area has a 30 percent chance of seeing rain?
THE SOURCES
- Brandon Gale, National Weather Service Austin/San Antonio meteorologist
- Bill Taylor, Chief Forecaster
THE ANSWER
WHAT WE FOUND
Here's what Gale had to tell us, "If we only think that's going to happen over 30% of the area, which is often the case once we get into the summer months, then we'll only say there's a 30% chance of rain just because of the coverage."
What it comes down to is the probability of precipitation. which is the likelihood of precipitation in the forecast area. That involves the confidence of rain and the area that will get rain. For example, in the KENS 5 region if there is an 80% chance of rain in 50% of the forecast area, the chance of precipitation where you live is 40%.
Chief weathercaster Bill Taylor agrees.
"It is a common misconception that people think it's 30% of the area gets rain now, 30% for everybody in that forecast area on a probability of getting rain. So that means there's a 70% chance you won't get rain," he said.
So yes, it is true. A 30% chance of rain means everybody in the forecast area has a 30% chance of seeing rain.
Both Gale and Taylor say many may be overthinking this. If you hear a 30% chance of rain where you live, think of it as isolated, and you might want to keep an umbrella handy. Anything from 40% to 60% and you can expect scattered showers. Anything from 70% and above, odds are, a raincoat or umbrella will be needed.