Build a Balloon Barometer

The Seasons

(Earth Science for ages 6+)

There are many tools and devices used to measure changes in the environment to help meteorologists (the weather people) make predictions about the weather.

Thermometers, rain gauges, and advanced technologies like radar are all important, but there is also a tool called a barometer that measures the pressure in the atmosphere.

Atmospheric pressure can indicate whether or not a storm may be on its way or if it is going to be a beautiful, sunny day. But what exactly is this pressure? Well, the atmosphere is a layer air that is about 300 miles thick and surrounds the entire surface of Earth.

This air is constantly pushing down on the earth, thus creating atmospheric pressure.The video above provides a simple tutorial to build your very own barometer at home and measure atmospheric pressure yourself. Here’s how it’s done:


1 clean jar
Rubber band
Marker pen
1 sheet of paper
Adult supervision (Adult supervision at all times please)


  1. Using the scissors, start by cutting the neck off of the balloon. Be sure the opening in wide enough to stretch across the opening of the jar.
  2. Make sure your jar is clean and dry. Stretch the balloon across the opening of the jar trying to make the surface of the balloon as flat as possible. Once it is stretched flat, use the rubber band to secure the balloon in place.
  3. If your plastic straw has a bendy section, first cut that section off. Attach the needle to one end of the straw using the tape. Be very careful when handling the needle so you don’t poke yourself.
  4. Use the glue to attach the other end of the straw (not the one with the needle) to the surface of the balloon. Now your barometer is ready.
  5. Using the marker pen, write “High” at the top of your sheet of paper, and “Low” at the bottom. (See the video for a good example of what this looks like.) Tape the sheet of paper to the wall and set your barometer next to it so that the needle points to the paper between “High” and “Low.” Preferably, this should be near a window for best results.
  6. With the pencil, mark the point on the paper where the needle points and label with “1” so you know this is the starting point. Leave your barometer undisturbed for several hours.
    Recheck the needle and mark where it points. Again, label this spot so you can keep track of how the needle moves over time. Recheck the needle every few hours. What do you notice about the placement of the needle over time? Is it changing a lot? What do you notice about the weather outside each time you check the needle?


A barometer measures the atmospheric pressure, also known as barometric pressure. This measure can tell meteorologists a lot about what sort of weather to expect. Typically, when barometric pressure is high, it tends to be nice outside with few clouds and lots of sun.

On the other hand, when pressure is low, it tends to be cloudy and rainy outside. So how does this move your barometer needle? When you cover the opening of the jar with the balloon, you trap air molecules inside at whatever pressure the atmosphere has at the time.

This is why it is important to mark the first position of the needle. If the pressure increases (nice, sunny days), there is more pressure outside of the jar than inside, so the balloon is slightly pulled inside, raising the needle.

If the pressure decreases (rainy and cloudy days), the pressure outside the jar is lower than inside, so the balloon slightly bulges out and lowers the needle. Pretty neat, huh?