A "30% chance of rain" in the UK means there is a 30% probability that measurable precipitation (usually at least 0.01 inches or 0.025 cm) will occur at any point in the forecast area during the specified time period, typically a day or part of a day
. This does not mean:
- It will rain for 30% of the time,
- Or that 30% of the area will definitely get rain,
- Nor that there is a 100% chance of rain over 30% of the area.
Instead, it reflects the confidence of the forecast combined with the expected coverage of rain. For example, if the forecast model runs 10 simulations and 3 of those suggest rain, the chance of rain is 30%
. It implies that in 30 out of 100 similar weather situations, rain would occur. In practical terms, if you are in the forecast area, there is a 30% chance you will experience rain at some point during the forecast period. Conversely, there is a 70% chance you will not get wet
. This probabilistic forecast helps convey uncertainty in weather predictions, especially in the UK where weather can be highly variable and localized
