Weather is the one branch of science where a child can collect real data every single day without leaving the garden. These weather experiments for kids cover cloud formation, pressure, wind, and rain — and most end with an instrument they built themselves.
Build Your Own Station
Four instruments cover everything a home station needs. Build them on the same weekend and start logging the following Monday.
| Instrument | Built from | What it tells you |
|---|---|---|
| Rain gauge | Cut bottle, ruler taped on | Millimetres of rainfall |
| Anemometer | Four paper cups, straws, pencil | Relative wind speed |
| Wind vane | Card arrow on a pin | Wind direction |
| Barometer | Jar, balloon, straw pointer | Rising or falling pressure |
1. Cloud in a Jar
Do it: pour warm (not boiling) water into a glass jar, place a lid or plate with ice cubes on top, and wait a minute.
You see: mist forms in the jar. Why: warm water evaporates, the vapour hits cold air near the lid, and it condenses onto dust particles — exactly how real clouds form.
2. Rain in a Bag
Do it: draw the sun and clouds on a ziplock bag, add a little blue water, seal it, and tape it to a sunny window.
You see: droplets form on the inside within hours and run down. Why: evaporation followed by condensation. The whole water cycle in one bag.
3. Tornado in a Bottle
Do it: fill a clear bottle two-thirds with water, add glitter, seal it, and swirl it in a circle.
You see: a spinning vortex. Why: swirling water is pushed outward, leaving a low-pressure core — the same shape a real vortex takes, though the forces are different.
4. Balloon Barometer
Do it: stretch a balloon over the mouth of a jar, glue a straw pointer on top, and mark a scale on the wall behind it.
You see: the pointer drifts up as pressure falls. Why: lower outside pressure lets the air inside push the balloon outward. Log it daily and it predicts rain surprisingly well.
5. Cup Anemometer
Do it: tape four paper cups to two crossed straws on a pencil that spins freely.
You measure: count rotations in 30 seconds. Why: faster wind pushes the open cups harder. You cannot get miles per hour without calibrating, but you can compare days.
6. Rain Gauge
Do it: cut the top off a bottle, invert it as a funnel, tape a ruler alongside, and set it in open ground.
You measure: millimetres per day. Why: a straight-sided container gives depth directly. Compare against the official local figure and see how close you get.
7. Dew Point on a Can
Do it: put a can of cold water outside on a warm day and watch the outside of the can.
You see: droplets appear. Why: the can cools the air below its dew point and water condenses out. Try adding salt to the water for a colder can and more condensation.
8. Evaporation Rate
Do it: two identical dishes of water, one in sun, one in shade. Mark the level and measure daily.
You see: the sunny one drops faster. Why: heat gives molecules the energy to escape. Add a third dish with a cover to test humidity’s effect.
9. Fog With Pressure
Do it: put a little warm water in a sturdy bottle, pump in air with a bike pump adaptor, then release the pressure suddenly.
You see: fog appears when the pressure drops. Why: expanding air cools, and cool air holds less vapour. Adult supervision only — never over-pressurise a bottle.
10. Static Lightning
Do it: in a dark room, rub a balloon on wool and bring it near a metal tap, or touch another person after shuffling on carpet.
You see: a small spark. Why: charge builds until it breaks down the air. Same mechanism as lightning, at a tiny scale.
11. The Month-Long Log
Do it: record temperature, rainfall, cloud cover, wind direction, and pressure at the same time every day for 30 days.
You get: a data set worth graphing, and the ability to check whether falling pressure really does predict rain where you live. This is the strongest of all these weather experiments for kids as a science fair entry.
Safety
- Never observe a real storm from outside — windows and indoor walls only, and no kites or umbrellas in thunderstorms
- Hot water for the cloud jar: warm from the tap is enough, an adult handles anything heated
- Bike pump experiments can be dangerous with glass or over-pressure; use plastic and release pressure gently
- Glitter and small parts are choking hazards for toddlers — keep them out of reach
Keep Exploring
- How do clouds form? — what experiment 1 shows
- What is the water cycle? — the bag experiment in context
- Weather vs climate — the distinction your log will raise
