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Make a DIY rain gauge from a plastic bottle in minutes! A simple weather science activity kids can use all spring to track real rainfall.
Rain is one of those things kids find endlessly fascinating – and with a homemade rain gauge, they can actually measure it. This DIY rain gauge uses a plastic bottle and a few supplies you probably already have, and once it’s built, your kid can track rainfall all spring long.
We made ours during monsoon season here in Arizona, when storms roll in fast and drop a surprising amount of rain (along with strong winds, lots of thunder, and lightning). I know, surprising for a desert, right?
Whenever my kids see black clouds roll in, they run out with their DIY rain gauge to measure the rainfall. They were shocked to see how much rainwater was actually collected every time!
What is a Rain Gauge?
A rain gauge is a device that measures the amount of precipitation in a given time period.
The top part of the device has a funnel-like opening that collects the rainfall and sends it down to an empty container below where it can be measured.
Rain gauges can collect data on how much water was collected, the rate at which it was collected, and the time it took to collect the rainwater. The rate at which precipitation accumulates is measured in inches per hour or millimeters per hour.
What Kids Learn from This Activity
This science activity is sneaky-educational. While your kid is out there checking the gauge after every storm, they’re actually practicing real science skills:
- Measurement – reading a scale in inches or centimeters
- Data collection – recording results over time to look for patterns
- Weather science – understanding precipitation and how meteorologists track rainfall
- Scientific method – making predictions before a storm and comparing them to actual results
- Math – comparing measurements, calculating totals, and eventually graphing data for older kids
How to Build Your Own DIY Rain Gauge
Supplies:
- Empty plastic bottle
- Pebbles or marbles
- Permanent Marker
- Ruler
- Pair of scissors or an X-Acto knife
- Tape
Instructions:
1. Cut the top off the bottle.
Use a pair of scissors or an X-Acto knife to carefully cut the top off the empty plastic bottle. Cut about 2 inches down from the top.
- Depending on the age of your child, you may want to do the cutting. If your child wants to cut, I highly recommend having him or her wear a cut-resistant glove to prevent any hand injury.
- We used a 500 ml bottle for our rain gauge because that was what we had at home. Depending on how much rain you predict to have, you may want to use a bigger bottle such as a 2L soda bottle or a 1L water bottle.
- It’s very difficult to cut perfectly around the water bottle. If you have frayed edges, you can trim them slightly.
2. Place pebbles or marbles in the bottom of the plastic bottle.
Whether you are using water bottles or soda bottles, the bottom of the bottle most likely is not flat. Filling up the bottom part of the bottle with pebbles or marbles will help even it out.
The weight of the pebbles will also keep the DIY rain gauge upright when there are strong winds.
3. Invert the top of the bottle and place it over the bottle opening.
Turn the top part of the bottle upside down so that when you put it over the bottle opening, the top is pointing downward. It will act as a funnel for the rain.
4. Tape the funnel to the bottle.
Use tape to secure the top of the bottle to the bottle. I recommend doing this step even if it feels like the funnel is fitting quite snugly in the bottle, because if the rain gauge tips, it might still fall off.
5. Label the measurements on the bottle.
Set the bottle on a flat surface. Mark the “0” line, which should be slightly above the top of the pebbles.
Place the ruler against the bottle and line up the “0” line to the 0 cm or 0 in mark on the ruler. Draw a vertical line. Use the permanent marker to mark off every centimeter or inch until you reach the top of the bottle.
Note: Depending on the height of your bottle, you may choose to mark off every half-inch, quarter-inch, etc. You can decide the right unit of measurement for your DIY rain gauge.
6. Pour water to the bottom mark.
Pour some water into the bottle until the water reaches the 0 mark.
7. Check the weather.
Now the most difficult part of this experiment – predict the weather!
During the monsoon season, the weather can change at any second. Check the news or websites like weather.com to get an idea of when rainfall might be arriving in your area.
This is also a good opportunity to go outside with your kids and observe the clouds. Sometimes, you can even see a storm on the way with lightning on the horizon.
8. Place the rain gauge outdoors to collect rain.
Go outside and put the DIY rain gauge in a nice, open area. You want to make sure there are no overhead obstructions, such as the roof, that could block rainfall.
If your rain gauge has been outside for a while without rain, you may want to double-check whether the water at the bottom is still at the 0 mark. On a hot day in Arizona, water can evaporate quickly. Pour more water into the bottle if necessary.
9. Record the amount of rain.
After the rain stops, check the rain gauge to see how much rain has fallen!
How to Track Your Rainfall Data
Building the gauge is the easy part. The real learning kicks in when your kid starts recording what they find.
After each rain, have them write down the date and the measurement before emptying the gauge. Even a simple notebook works great for this. Over a few weeks, patterns start to emerge – which storms dropped the most rain, which months are the wettest, how your backyard compares to the official weather report.
For older kids, this turns naturally into a graphing project. Plot each measurement on a line graph, and you’ve got a real data set to analyze.
Take It Further: Build a Mini Weather Station
Once your kid has a rain gauge outside, it’s hard to stop there. You can turn the backyard into a full weather station with just a few more simple projects.
Pair the rain gauge with a weather journal. On rainy days, have your kid sketch the type of cloud before the storm hits and see if they can predict what’s coming. It’s the same thing meteorologists do, just with way more enthusiasm and fewer satellite images.
You can also explore where all that rain comes from in the first place. Our rain cloud-in-a-jar experiment demonstrates the water cycle in about ten minutes, and it’s a perfect lead-in to a conversation about why some storms drop half an inch while others barely register.
And if your kid wants to understand the bigger forces behind weather patterns, the cloud-in-a-jar experiment shows how temperature and pressure interact to form clouds, which suddenly makes the rain gauge data feel a lot more meaningful.
Final Thoughts on the DIY Rain Gauge
We tested ours through several storms last monsoon season, and the rocks held it steady through some serious wind. My kids checked it after every rain like it was the most important scientific data of the day – which, honestly, it kind of was.
If your kid catches the weather bug, don’t stop here. Our tornado-in-a-bottle experiment takes about five minutes to set up and always gets a reaction.
Let me know in the comments how much rain you collect this spring. I love seeing what different parts of the country get!
For more fun weather activities, check out:
I can’t wait for the results of my rain gauge! Thanks for the instructions.