Myth buster: what does the % of rain really mean?

A common question we get asked is what does the percentage of rain really mean in a weather app? Well, we’re here to debunk the misconceptions.

A viral video recently did the rounds on TikTok about what the percentage of rain really means on a weather app.

The video claimed that when you see the percentage of rain, it doesn’t actually mean the chance that it will rain, but rather the proportion of land that will see the rain.

So, hypothetically, if there's a 30% chance of rain on a weather app, it would mean only 30% of the forecast area will see rain, rather than there being a 30% chance of it raining altogether.

Another misleading assumption is that the percentage indicates the amount of time it would be raining for, in relation to the forecast period, e.g. 30% of the one hour time period.

Spoiler alert: neither method is widely accepted by Meteorologists to calculate the probability of precipitation!

Far more commonly used, is just the good, old-fashioned probability of you seeing rain at that time, in your forecast area, and that’s exactly the method on our Weather & Radar app too.

A 30% chance means a 30% chance that it will rain in your forecast area, and a 70% chance that it will stay dry.

When there are showers in the forecast, rather than a solid band of rain, there is a great deal of uncertainty. This is because showers can be extremely localised, forming and dissipating over short time periods.

Often with showers, the chance of precipitation could be fairly low, but the risk could be throughout the entirety of the day.

So, if you’re unsure about whether you’re at risk of catching a shower, stay updated via our WeatherRadar, where you can see where the showers are developing real-time.