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How does a rain gauge work? Measure the rainfall over a period of time and compare it with the daily weather reports. – Principles of cloud seeding and other weather modification.

Introduction: (Initial Observation)

The water that we drink and use for washing and bathing has been in the form of rain drops at some point. Rain refills dams and lakes and underground waters. Rain also irrigates farms and forests. In the history of mankind, many lakes and rivers have dried, many towns and villages are abandoned, many human and animals have died because of drought.

Drought is a long period of abnormally low rainfall, especially one that adversely affects growing or living conditions.

Because of the importance of the rain in our lives, meteorologists constantly monitor, measure and record the rainfall. In this project you will make a rain gauge. You will then use it to measure rainfall over a period of time and compare it with daily weather reports.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Warning: Adult help and supervision is required for some experiments, specially when hazardous material, electricity or sharp objects and tools will be used.

Information Gathering:

Learn about rain and how it forms. Read books, magazines or ask professionals who might know in order to learn about water cycle and production of rain. Keep track of where you got your information from.

You may find statistic or data about your local rain from


Rain data is also published in local newspapers.

Cloud seeding (also known as weather modification) is the deliberate treatment of certain clouds or cloud systems with the intent of affecting the precipitation process(es) within those clouds. Application of this technology is increasing world-wide.

Cloud seeding materials are released via ground-based and/or airborne systems. Determination of the best suited method or combination of methods for a given project is based upon an assessment of a variety of factors. The seeding materials are applied to the clouds (sometimes targeted very carefully into very specific portions of clouds) so that the material has adequate time to affect the precipitation process, so the effect will be focused over the intended geographic area.

  • What are the most commonly used seeding materials?

The materials used in cloud seeding include two primary categories, tied to the type of precipitation process involved. One category includes those which act as glaciogenic (ice-forming) agents, such as silver iodide, dry ice and compressed liquid propane or carbon dioxide, which are appropriate in cloud systems where the precipitation process is primarily cold (colder than freezing). Of the ice-forming materials, the most commonly used is silver iodide. The second major category is focused on cloud systems where the warm (coalescence) process predominates. In those environments, hygroscopic (water attracting) materials such as salt, urea and ammonium nitrate can be utilized. Of the hygroscopic materials, the most commonly used are salts.

Learn more about cloud seeding visit:



Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

How accurate are rainfall data? Does a personal recording of rainfall produce the same results as data collected and reported by weather agencies?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

The independent variable (also known as manipulated variable) is the date or the day of the year.

Dependent variable (also known as responding variable) is the amount of rainfall in that day.

Controls variables are the location of the experiment and the method of experiment (rain gauge).


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. This is a sample hypothesis:

The amount of daily rain recorded at home is the same or very close to what is being reported by weather agencies.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1:

How rain is made?

Water evaporates and forms clouds. Clouds move by wind until they hit a cold air. That’s where water moisture condense and comes back to the earth in the form of rain or snow. The following procedure shows how does this happen.


Ask your mom, dad or teacher to help you with this experiment. (Do not try it by yourself!)

  1. Boil water until steam rises.
  2. Hold a tray of ice about 5 inches above the steam. Use potholders to protect your hands from the hot steam.
  3. Continue holding the tray until drops form on the bottom, get heavy and fall like rain!

Experiment 2:

Make a rain gauge

A rain gauge is an instrument for measuring the amount of rain. Rain is measured by centimeter, millimeter or inches.

Almost any cylindrical container can be used as a rain gauge. In a cylindrical container, the area of the mouth of the container is the same as the area of the bottom of the container. If after one hour we accumulate one inch rain water at the bottom of the container, that shows that we have had one inch rain in one hour. The problem is that if we can not make continues observation, this water may evaporate and disappear in the next few hours. For example water accumulated by a morning rain may disappear by the afternoon.





To avoid this problem, a better rain gauge must somehow protect the collected rain. Insulation on the sides and white paint can reduce the effect of heat. A cap or funnel on the top can also reduce evaporation.
Another simple cylindrical rain gauge is just a measuring cylinder also known as graduated cylinder. These type of rain gauge are also available commercially with decorative bases. Since the mouth of a graduated cylinder is not wide enough, the accuracy of measured rain will be much lower than wide mouth rain gauges.

Most professional rain gauges have a wide mouth funnel on the top. Such rain gauges collect rain drops from a wider area and direct it to a container on the bottom. They may also automatically drain rain water after measuring it by a mechanical or electronic system.


Inexpensive Simple Rain gauge

Simple design graduated rain gauges made of clear plastics are very common among students who need a quick way of measuring the rain.

You can order one online from MiniScience.com.


What You Need

  1. Plastic ruler
  2. Scissors
  3. Clear Waterproof Tape
  4. Glass wide mouth jar with wide bottom (suggest a quart jar)


  1. You might cut the ruler in half so you can measure rain up to six inches. The six-inch ruler will fit better in your quart jar, too!
  2. Place the ruler inside the jar. Tape the ruler in place.
  3. When it is going to rain, place your jar in an open area where it can collect rain. Don’t put the jar near or under trees or near buildings.
  4. After it rains, see how much rain actually fell. Try to measure to the nearest tenth of an inch.
  5. You may want to record the amount of rainfall you get for several rains. You could keep track of rainfall for an entire month. To determine how much total rain you had for the month, add up all the measurements.

It is fun to record rainfall for several months. See if the amount changes with different months and seasons.

You may print your own ruler and cover it with clear plastic or plastic tape so it can resist the rain water.

To print the ruler click on that with right mouse button and select print picture from the menu that pops up.

What Is Happening

You can study many things about your own weather. One thing you can easily do is make a rain gauge and track the amount of rain you get in different storms or in different months of the year. With this information about rainfall in certain months, what kinds of activities would be best suited for different months? When would you plan outside activities? When would you plant gardens and fields? Check out other information to learn more about the weather patterns in your area. What kinds of things are happening in the atmosphere that impact the amount of rain you get during different times of the year?

Record your results in a table like this.

Date Inches of rain
(or millimeters of rain)

Experiment 3:

Make a tipping bucket rain gauge

Introduction: To have a more accurate data of rainfall in an area, you will need many rain gauges distributed in the area. Making daily observations of so many rain gauges is hard or often impossible. Because of this problem we will need a rain gauge that can record the rain data or transmit the rain data to a remote observation center. This need resulted the invention of tipping bucket rain gauge (by Christopher Wren in 1662).

In a tipping bucket rain gauge, Rain enters gauge through an orifice or large funnel. When a given amount of water collects, bucket tips (amount determined by calibration). Second bucket positions under funnel for filling. Any tipping bucket triggers a switch that creates a signal to a recording device.

In this experiment you will make the tipping bucket rain gauge without it’s electronic components.

Material: You can make a tipping bucket from plastic, metal or wood. The problem with wood is that it will get soft and changes it’s shape when in contact with moisture or water. Since I only had some balsa wood for my experiment, I decided to overcome this problem by painting my bucket with water resistant paint. Cutting balsa wood is easy. You first draw the lines and then trace the lines once or twice by a utility knife.

You may use a piece of 7″ x 1.5″ rectangle as the bottom of the bucket. You will then need two rectangles for the sides and one divider for the center to separate the left bucket from the right bucket. You can use regular wood glue to construct the buckets and use masking tape to hold the pieces together while you are waiting for glue to dry.

Wood glue takes a few hours to dry. You may use hot melt glue and a glue gun for faster results.

When the buckets are ready, glue a wood dowel under the buckets. Make sure it is centered and it is right under the divider piece.

When all glues are dried, paint the wood with any water resistant paint. You may repeat painting a few times. When your bucket is ready, you must mount it on a stand such that it can tip to the left or right. The height of the stands can be 1.5″ or more.

Get a piece of wood as base board and mount your stands on that. I used a pair of short wood dowels as stand. Wider pieces such as wood blocks work better than wood dowel. By now your tipping bucket should almost look like a see saw. If the stands are excessively tall, you can use additional wood blocks on the base board to restrict the movements of the tipping buckets. These blocks also simulate any possible switches in a real rain gauge.



When your tipping bucket is ready, you may test it by mounting a funnel above that and and pouring water in the funnel.


In a real rain gauge this whole setup is covered such that rain can only enter the buckets through the funnel.

Materials and Equipment:

List of material can be extracted from the experiment section. I have used whatever I could find around. You may modify the material and design based on what you have or you can find.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


No calculation is required.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Write if your experiments confirmed your hypothesis. If not, you will need to reject your hypothesis and find an explanation for that.

A common explanation is that weather agencies record the rain in many different weather stations across a state. They will then take an average of the total rain fall and report it. An average rainfall of a state vary from the rainfall in one location.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Is there any relation between the rainfall and temperature data?

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


List of References