Rain gauges
Standard rain gauge
Our standard instrument for measuring rainfall is a 203 mm rain gauge.
This is a circular funnel with a diameter of 203 mm. It collects the rain into a measuring cylinder.
The measuring cylinder is graduated and calibrated. It can record up to 25 mm of rain (precipitation).
Any excess precipitation is captured in the outer metal cylinder. The top of the rain gauge is 0.3 m above the ground.
Rain gauges in automatic weather stations
Automatic weather stations have a tipping bucket rain gauge. This also has a 203 mm opening.
Water is collected in small brass buckets, which tip as they reach their calibrated capacity. This generates an electronic pulse. The tipping point is equal to 0.2 mm of precipitation.
This type of gauge never needs to be emptied. It automatically reads the amount of rain and the rate at which the rain is falling.
Rain recorded on clear days
Sometimes a tipping bucket rain gauge will record rainfall when there is none.
This may happen because 0.2 mm, or a single tip of the bucket, can happen for other reasons. For example:
- vibration, sometimes caused by wind gusts, can tip a bucket that already contains a little water
- dew, mist or sea spray adding to water from a previous rain event.
Top view of a tipping bucket rain gauge and data logger, showing the tipping bucket device in the centre. Credit: Mike Rosel. Copyright Commonwealth of Australia.
Rainfall observations
Daily rainfall is officially measured each day at 9 am local time.
Some manual rainfall stations report 48 or 72 hour totals, or occasionally longer, if an observer can't attend. These are called accumulated observations.
At most sites, observations are taken by volunteers. They send in a monthly record of daily precipitation at the end of each month. Some send their observations electronically to us each day.
Rainfall is traditionally measured to the nearest 0.2 mm – 1 point, or 1/100th of an inch before 1970. Some observations are now reported to 0.1 mm. Any moisture less than this is recorded as a trace.
For more about reading observations tables, view our Observation details page.
Snow gauges
A snow gauge is used to measure precipitation at several locations within Australia where snow falls.
There are 2 types of snow gauges. They both melt the snow to measure the amount of fluid.
- Type 1 melts the snow using an electric element such as a light bulb.
- Type 2 melts the snow that falls into a tank containing an antifreeze agent.
A conical wind shield called a Nipher Shield may also be used to prevent vertical wind eddies and better capture snow falling over the gauge.
Measuring snow depth
The Bureau does not measure snow depth. It's very difficult to measure because snow density varies greatly from place to place.
Density depends on:
- the structure of the ice crystals
- how they have accumulated
- what shape they take
- how they stack when reaching the ground.
To estimate long term average precipitation, about 1 cm of fresh snow equals 1 mm of water.
Snowy Hydro has measured weekly snow depths at Spencer's Creek in New South Wales since 1954. Many resorts also record snow depth within their ski areas.
Taking your own observations
Selecting your gauge
You can buy a rain gauge from hardware and special interest stores, or make one from online tutorials. The Bureau doesn't provide instructions for making rain gauges.
Our standard rain gauge has an opening 203 mm in diameter. Using a rain gauge with a larger diameter may mean it collects a larger amount of rainfall.
Gauges with too small an opening:
- may be difficult to read when the rainfall amount is small
- are affected more by the wind
- may become blocked with debris.
Installing a rain gauge
Location
Gauges near buildings, solid fences and trees may be inaccurate.
Place your gauge at a distance that is:
- at least twice the height of any obstruction
- preferably 4 times the height. For example, more than 10 m from a house 5 m high and more than 30 m from the nearest branches of a 15 m-high tree.
Make sure it will not be disturbed by people, animals or vehicles.
Height
Higher gauges are more affected by wind. Wind speed generally increases with height above the ground. It can affect accuracy.
The top of the collector on our rain gauges is 0.3 m above ground level.
Secure and level
Make sure:
- the opening is horizontal
- surrounding grass and vegetation is not more than a few centimetres high
- the rain gauge is securely fastened, so that it won't blow over in strong storms.
Making a rainfall observation
Ideally, read the rain gauge as near to 9 am local time as possible.
During heavy rain you may need to read and empty the gauge more often, to prevent it from overflowing. Add the discarded amount to your next 9 am observation.
Reading your gauge
Make sure the gauge is vertical.
Bring the surface of the liquid in the gauge to eye level.
Read the position of the liquid surface against the scale. Make sure you read the bottom of the liquid surface and not the meniscus. The meniscus is the slightly higher lip where the surface meets the cylinder wall.
If the surface is midway between 2 divisions, use the higher division.
Snow or hail in the gauge
You'll need to melt any snow or hail in the gauge. You can do this in 2 ways:
- place the gauge in warm water
- add a measured quantity of warm water to the gauge. Subtract this amount from the total contents after it has melted.
If your records don't match Bureau rainfall observations
If observations from your gauge differ to the Bureau's official records, this may be due to:
- different location and surrounding site
- official rain gauges are made to exact specifications and fully calibrated
- timing of rainfall – rainfall observations are recorded as the total from 9 am to 9 am, and the amount is recorded on the date the rain gauge was checked. This is not necessarily the date on which the rain fell.
Providing observations to the Bureau
For information about volunteering as a weather observer, see our Observation network page.
Flood and river gauges
A range of gauges are used to measure river heights and flood levels.
Floods are a serious risk to life and property. The requirements for these gauges and reporting water levels are carefully managed.
Learn about flood classifications and river heights.
Our service agreements with state and territories outline the river heights that trigger watches and warnings. For details, view our Flood warning services page.
Find out about national guidelines and standards for water information, monitoring and flood warning. This includes:
- standards for flood warning infrastructure
- national guidelines for hydrometric monitoring – that is, observing and recording water levels.