If you always find yourself caught in the rain without an umbrella with you, you might be misreading the weather forecast on your phone. Many people think that a percentage like “30% chance of rain” it indicates the intensity of rain or the area over which it will rain, but meteorologists say the interpretation is wrong.
Dr Rob Thompson, a meteorologist at the University of Reading, explains that “30% chance of rain” it simply means that there is a three in ten chance that rain will occur during the forecast period.
“30% could mean either a torrential downpour throughout the forecast range or a brief five-minute downpour right at the end,” he specified for the platform Which?.
Experts recommend that you don’t just focus on the sun or cloud symbols used by apps, but check the actual hourly and daily rain chance percentages. For example, BBC Weather can show a rain cloud even when the chance of rain is 50% or less. Even if it doesn’t rain, the forecast was technically correct, because there was still a 50% chance that it wouldn’t rain.
Another common myth is that a forecast applies to the entire area. Weather apps divide the country into large grids of up to 200 km, and if rain is forecast in that grid, a rain symbol may be displayed even if there is no rain in your area.
Three tips to have a more accurate forecast
1. Use multiple weather apps – each app has strengths and weaknesses for different aspects of the weather.
2. Enable precise location on your phone – weather forecast is location dependent.
3. Watch the forecast on TV – the meteorologist interprets the data on the map and provides information that is easier to understand.
So the next time you see “30% chance of rain”, you know it doesn’t necessarily mean a light rain or that it will only rain on one side of the city, but simply that there is a probability that rain will occur.
