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Clearing up the ‘patchy rain’: introducing a more precise forecast language

Updated 24 August 2018

You probably read or hear the weather forecast almost every day, but what do all those terms actually mean? To make rain forecasts more helpful, the Bureau now uses more precise terminology.

How many times have you read or heard on the radio that there’ll be scattered showers or patchy rain where you live or work? How much does this information really help you—especially if you’re about to hang out the washing, or are trying to decide whether to take an umbrella to the office?

As the Bureau’s weather information has become more detailed and precise, the language of our forecasts has followed suit—we changed the way we describe the likelihood of rain, to ensure that our forecast descriptions are every bit as clear and precise as our graphical services. Forecasts now tell you if the chance of rain in your area is slight, medium, high or very high at different times of the day, with a percentage equivalent.

For example, here's a forecast for Sydney and the surrounding area:

The left side of the forecast provides the temperatures, possible rainfall amounts and the chance of any rain for Sydney's city centre.

The right side elaborates on these figures with a statement such as a ‘High (70%) chance of showers’. Sounds like umbrella weather, doesn’t it?

Let’s explore this a bit further. ‘High’ relates to a simple scale of how likely you are to receive rainfall in that forecast area. This scale is shown in the table below:

Chance of rain Terminology used 0%, 10% No mention of rainfall in forecast 20%, 30% Slight (20%) chance of… Slight (30%) chance of… 40%, 50%, 60% Medium (40%) chance of… Medium (50%) chance of… Medium (60%) chance of… 70%, 80% High (70%) chance of… High (80%) chance of… 90%, 100% Very high (90%) chance of… Very high (near 100%) chance of…

This simple information is probably enough to tell you how likely you are to get wet and whether you need a raincoat. But what else can you tell from the forecast?

Timing of rainfall: If the chance of rain is confined to a short period of the day, you may see words such as ‘most likely in the morning’.

Heavy rainfall: If very heavy rainfall is a possibility, you may see words such as ‘Showers, heavy at times’. This one might be a useful warning to check that those gutters are clear.

Thunderstorms: If there is a chance of thunderstorms during the day, this will be mentioned.

Other weather: When appropriate you will also be advised of other weather phenomena, such as hail, frost, fog or snow.

So there you have it. This forecast terminology will help you make important decisions about your outdoor activities every day.

More information

How to interpret the chance of rain percentage

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