What does a Rain Gauge Measure and How It Works

Measuring rainfall is a long-drawn practice first performed as back as the 4th century. Records were kept even then for comparing and weighing through various methods. It was in the 13th century that the mechanism of "rain gauge" was invented. Since then, the fundamental unit of rain gauge has been developing across different regions in different ways. However, the concept and purpose remain the same.

how does a rain gauge work

You can't find any other instrument except the rain gauge that can measure the amount of rainfall. This is one of the most reliable and easy-to-use instruments that you can easily get and avail of its benefits. Before getting in-depth about the functionality of the rain gauge, we'll move gradually and understand what is rain gauge at the first place.

What is Rain Gauge? 

Rain Gauge is a meteorological instrument that is used by meteorologists and hydrologists to measure the rain precipitation in a given amount of time per unit area. It is also known by the names of udometer, pluviometer, and ombrometer. 

The instrument has an unembellished design that consists of a collection container that is placed in an open area that will serve the purpose of a recipient. While collecting the rain in this small container is assumed that the same amount of rain precipitation is occurring all around the container. Hence, the area covered by the container does not make any difference in the final calculation.

Even so, the container should be of adequate size, being neither too small nor too big. The precipitation is measured in millimeters(mm).The rain gauge can be of different types, the most popular design being a standard cylindrical vessel. It has been made in such a way that the container does not allow the water to be evaporated before the measurement has taken place. 

Within a large geographical area, standard instruments are used in each region to avoid any sort of discrepancies, as it may eventually lead to faulty large-scale observations. This job of designing a standard rain gauge is given to the World Meteorological Organization, which plays an effective role in providing standard designs that are expected to be opted by everyone.

best rain gauge

Oregon Scientific Wireless Rain Gauge

  • 300 feet transmission range
  • Stores ecorded rainfall data of last 10 days
  • Records rainfall upto 0.4 inches
  • Thermometer to measure temperature
  • Stylish design that blends with garden décor

Why is Rain Measured in inches

Using inches as a measurement unit for rainfall is a convenient way to read the rainfall readings accurately. This approach is popularly used in the US to make the readings more reliable and efficient.

By saying the inches as metric units for rainfall measurement, we try to interpret the inches in the storm or the inches in the last 24 hours observed in the rainfall. Or, more specifically, with the inches, you can say how many inches are observed in some particular period.

But, what is 1 inch of rain? Is it something new or different? You can understand 1 inch of rain as it is much more in 15 minutes than the 1 inch of rain observed in the last month.

Do you know that 1 inch of rain is so powerful that it can even cover the entire ground if it doesn't assimilate with other water bodies like lakes or rivers and stays in a single place? Isn't it amazing!! If we see in figures, then 1 inch of rain can be described as a value equivalent to 4.7 gallons of water per square yard,

How is rain measured in inches

You must be wondering that how the rainfall is measured in inches? Well, that is simple. You have to check the measurement scale in the cylindrical glass concerning the water level.

The main rain gauges come with a wide funnel that ultimately takes the rainwater to the cylindrical opening, which is calibrated as one-tenth of an inch of rain.

This calibration plays a vital role in measuring one inch very easily when the rainwater is collected inside the gauge. With the help of inches calibration, it becomes very easy to read even highly precise values.

Types of Rain Gauges

Rain Gauges fundamentally measure the rain precipitation, and there are several types of rain gauges, each one performing differently. Yet one thing can be assured that from all the methods, you will get a near accurate intel on the amount of rainfall in your area.

Although there are several kinds of rain gauges in general, some of them indigenous mechanisms which occur only in certain specific regions, there are three broad types of rain gauges. They are:

  • Standard Rain Gauge,
  • Tipping Bucket Gauge
  • Weighing Gauge.

How Does a Rain Gauge Work?

Each type of gauge performs its primary function of rainfall recording and a few distinctive functions. Let us discuss this in detail. 

Working of Standard Rain Gauge: 

Working of Standard Rain Gauge
  • This gauge for measuring rainfall is used so widely that even meteorological departments have opted for this method. In this mechanism, an 8-inch diameter funnel-shaped or cylindrical collected is linked with a measuring tube and is placed in an open area where it can receive rain.
  • This design is further kept into a larger outer container in case the inner container starts overflowing. Although there is no clearly defined size of the collector mentioned in any of the WMO pamphlets, it has been advised that the collector should neither be too small nor too big. Rainfall is generally measured by measuring the height of the water in the inner cylinder.
  • The excess water collected in the outer container is poured into another container wherein the measurements are further taken. This gives one the total rainfall. 
  • Some measures are taken to avoid any kinds of leakage, so the observations are not contaminated in any way. The rain gauge performs its function by magnifying the rain by a factor of 10. Magnification of rain helps in attaining accurate measurements.

Working of Tipping Bucket Rain Gauge: 

Working of Tipping Bucket Rain Gauge
  • The operation of a tipping bucket rain gauge is completely different from the standard rain gauge. While the design of the standard rain gauge is simple and unembellished, the design of the tipping bucket rain is considerably more comprehensive. Even the accuracies of both differ with standard rain gauge being slightly more accurate.
  • The design of the tipping bucket rain gauge is that of a seesaw. You have a funnel that collects the rain and transfers it to a different small container. 
  • This design may underestimate heavy rain when a definite amount of rain is caught by the funnel, the shaft tips, and does the trick of measuring the amount. This may not give accurate figures because if rainfall stops before the shaft moves, you may get faulty data.
  • The distinctive feature of the tipping bucket rain gauge is its tendency to estimate the nature of the rain, that is, if the rain is light, medium, or heavy. The basic design of Tipping Bucker Rain Gauge has developed over time, like any other rain gauge, but the underlying mechanism remains the same.

Working of Weighing Rain Gauge:

Working of Weighing Rain Gauge
  • A weighing gauge is a unit consisting of a storage bin that is used to record the mass. The mass is measured using a rotating drum-like object, and this design is considered best for climatology use, as recognized by the New York National Weather Service office.
  • These gauges are accurate in measuring the intensity of rainfall, which is why it is considered better than the tipping bucket rain gauge. The weighing mechanism of the weighing method allows you to measure the time and depth both at the same time.
  • Unlike the tipping bucket rain gauge, the weighing gauge can also measure other forms of precipitation, such as hail and snow, which is why they are more expensive and high-maintenance.

How do Meteorologists Measure Rainfall

Meteorologists are the experts who can measure the rainfall levels with utmost accuracy and precision levels. But, you must be wondering that how they can measure the rainfall? Is there anything special that they possess? Need not worry as we will address your concern, and you can easily know how they measure the rain.

The most basic concept used for measuring rainfall levels is to find the rainfall depth during a specified period. But the professionals opt for complicated devices like tip bucket rain gauges that they employ to measure the rainfall. This instrument consists of two buckets placed beneath the funnel.

When the rainfall starts, then by crossing the passage of the funnel, the first bucket starts filling, and it usually gets filled after 0.2mm of rain. Once this bucket is filled, the tip shifts to another bucket, and this process repeats recursively.

The rain gauge keeps a tab of the tips during the rainfall to maintain a proper record. This data helps to find the meteorologist that how quickly does the rainfall is for a specific time. So, this is how the professionals measure the rainfall levels.


Measuring rainfall has become essential for the follow-up proceedings, such as determining the climatic conditions of a region and weather forecasts. Due to so much depending upon the measurement of rainfall over an area, it is essential to have precise data. Faulty data may lead to other faulty observations.

Thus, choosing an accurate means of measuring rainfall is essential. The Standard Rain Gauge has been credited by the World Meteorological Organisation, and also the meteorological departments across the states have recognized it as the most accurate and precise mechanism.

Related Posts

About the Author


I am Tim, a weather enthusiast who loves to watch hurricanes and all other harsh weather conditions. I studied B.Sc(Meteorology) at the University of Miami. With excellent knowledge of Weather Forecasting, Meteorology, and Environmental Science, I am currently working in San Francisco as a Meteorologist. Also, I am a member of The Weather Channel and AccuWeather. In this blog, I will write a detailed review of Weather instruments that you need for survival and other activities.