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Live forecasts update automatically; written guidance last reviewed 14 June 2026 by the StoryShift weather desk. Data from national met services via Open-Meteo.
The rain percentage you see in a weather forecast is the probability of precipitation (PoP) — the likelihood that at least 0.01 inches of rain will fall anywhere within the forecast area during that time window. It does not tell you how hard or how long it will rain.
What does the percentage of rain actually mean?
When a forecast says “60% chance of rain”, it means that over the past 10 years, under similar weather conditions, measurable rain fell 6 out of 10 times in that specific location at that time of day. This is known as the probability of precipitation (PoP). A common misunderstanding is to interpret the figure as how much of the area will get rain, or how intense the rain will be. Neither is correct — it is purely a statistical probability.
How is the rain percentage calculated?
Forecasters use a simple formula: PoP = Confidence × Area. First, they estimate how certain they are that rain will occur somewhere in the region (confidence, expressed as a decimal). Then they multiply that by the proportion of the region expected to receive measurable rain (area, also a decimal). For example, if forecasters are 80% confident and believe 50% of the area will be affected, the PoP becomes 40%. The final figure is rounded to the nearest 10% for simplicity.
What does a 20%, 60% or 90% chance of rain mean for your day?
A 20% probability means rain is unlikely — you may want to keep a light jacket handy but probably do not need to change plans. At 60%, conditions are favourable for rain; carry an umbrella if you are heading out. A 90% or 100% chance of rain means nearly certain precipitation — it is wise to postpone outdoor activities or dress accordingly. Remember that even with a low percentage, isolated showers can still catch you out; check the 10-day forecast for context.
Does the percentage of rain mean the area covered?
No, despite a widespread belief, the rain percentage does not tell you the share of your region that will get wet. The “area” component of the formula is a forecaster’s estimate of coverage, but the final PoP number combines it with confidence. A 50% PoP could come from 100% confidence that 50% of the area will get rain, or 50% confidence that 100% of the area will get rain — the public sees only the product. That is why the same percentage can feel different on different days.
What does the percentage of rain mean on iPhone and other apps?
Most smartphone weather apps — including the default iPhone Weather app — source their percentage from the same national meteorological data, typically the Met Office or Apple’s own weather provider (now derived from Apple Weather). The figure displayed is the PoP for your saved location. However, some third-party apps may show “precipitation probability” alongside separate “intensity” bars. Always check the source and read the app’s help section to understand exactly what they display. For official UK forecasts, the Sources & Standards page explains data providers.
What does the percentage of rain mean for the Met Office?
The Met Office uses PoP exactly as described above. Their forecasts state “chance of precipitation” for each three-hour period and for days ahead. If you see “60% chance of rain” for today, the Met Office means there is a 60% probability that a rain gauge at your location will record measurable rainfall during that period. They do not use area coverage as a direct figure. You can check live updates at the UK weather hub.
Frequently asked questions
Does 100% chance of rain mean it will definitely rain?
Yes, effectively — a 100% PoP means forecasters are certain that measurable rain will fall somewhere in the forecast area during the period. However, it does not guarantee that it will rain at your exact location, nor does it tell you how heavy the rain will be. In practice, you should expect rain and plan accordingly.
What does the percentage of rain mean on a weather app?
Most weather apps show the probability of precipitation for your chosen location. This is the same PoP figure described above: a statistical probability, not a measure of area coverage or intensity. Some apps also display separate bars for rain intensity (light, moderate, heavy) to give a fuller picture.
What does the percentage of rain mean today compared to a weekly forecast?
The percentage for today is based on higher-confidence short-term models, so it is more reliable. For later days in the weekly forecast, the PoP is derived from ensemble models with lower confidence. A 40% chance five days out may well change, while a 40% chance this afternoon is more dependable. Always refer to the 10-day forecast for trend, but rely on near-term PoP for decisions.
Does the percentage of rain mean the area that will get wet?
No — see above. The figure confuses many people because early weather presentations sometimes implied coverage. Modern meteorology uses a unified probability definition. If you see “60% chance of rain”, it does not mean 60% of your town will get wet; it means a 60% chance that you will get wet at your location.