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Anne Marie Helmenstine, Ph.D.

Make a Simple Weather Barometer

By May 13, 2013

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It's easy to make your own weather barometer. (Anne Helmenstine)People predicted the weather back in ye good olde days before Doppler radar and GOES satellites using simple instruments. One of the most useful instruments is a barometer, which measures air pressure or barometric pressure. You can make your own barometer using everyday materials and then try to forecast the weather yourself.

Barometer Materials
  • glass, jar, or can
  • plastic wrap
  • a straw
  • rubber band
  • index card or lined notebook paper
  • tape
  • scissors
Construct the Barometer
  1. Cover the top of your container with plastic wrap. You want to create an airtight seal and a smooth surface.
  2. Secure the plastic wrap with a rubber band. The most important part of making the barometer is getting a good seal around the rim of the container.
  3. Lay the straw over the top of the wrapped container so that about two-thirds of the straw is over the opening.
  4. Secure the straw with a piece of tape.
  5. Either tape an index card to the back of the container or else set up your barometer with a sheet of notebook paper behind it.
  6. Record the location of the straw on your card or paper.
  7. Over time the straw will move up and down in response to changes in air pressure. Watch the movement of the straw and record the new readings.
How the Barometer Works

High atmospheric pressure pushes on the plastic wrap, causing it to cave in. The plastic and the taped section of straw sink, causing the end of the straw to tilt up. When atmospheric pressure is low, the pressure of the air inside the can is higher. The plastic wrap bulges out, raising the taped end of the straw. The edge of the straw falls until it comes to rest against the rim of the container. Temperature also affects atmospheric pressure so your barometer needs a constant temperature in order to be accurate. Keep it away from a window or other places that experience temperature changes.

Predicting the Weather

Now that you have a barometer you can use it to help predict the weather. Weather patterns are associated with regions of high and low atmospheric pressure. Rising pressure is associated with dry, cool, and calm weather. Dropping pressure forecasts rain, wind, and storms.

  • Quickly rising pressure that starts from average or high pressure during fair weather indicates a low pressure cell is approaching. You can expect the pressure to start to fall as poor weather approaches.
  • Quickly rising pressure (over a few hours or a couple of days) after a period of low pressure means you can expect a short period of good weather.
  • Slowly rising barometric pressure (over a week or so) indicates good weather that will stick around a while.
  • Slowly falling pressure indicates the presence of a nearby low pressure system. Changes in your weather are unlikely at this time.
  • If the pressure continues to drop slowly you can expect a long period of bad (as opposed to sunny and clear) weather.
  • A sudden drop in pressure (over a few hours) indicates an approaching storm (usually arriving within 5-6 hours). The storm probably involves wind and precipitation, but won't last long.

Make a Weather Glass | Does Atmospheric Pressure Affect Humidity?

Comments

November 24, 2008 at 10:02 am
(1) Josh says:

great!thanks for the idea!

May 4, 2009 at 5:45 am
(2) jericho says:

it’s a great idea
because you use only plastic wraps instead of balloons.
it’s impressive……….
and a great, impressive and a fun science project

August 20, 2011 at 9:00 am
(3) Wilson Sew says:

I used a graph paper instead of a lined paper. =)

June 10, 2009 at 6:02 am
(4) ashmita says:

hey!thanks for this idea,as this will help me as my science holiday project!!!Please send me such ideas !!!

August 29, 2011 at 7:01 am
(5) evelyn says:

hi Dr. Helmenstine, that was a great, easy to work on i will try it at home! more power.

December 16, 2011 at 1:56 pm
(6) julia and haruhi! says:

thanks for the idea, we will use this in science class.

May 15, 2012 at 6:12 pm
(7) twitbaily says:

Thank you so much for this!!!

May 19, 2012 at 11:18 am
(8) vanshika says:

nice work Dr.

October 7, 2012 at 3:24 am
(9) chiranjeev singh says:

great!thanks for the idea!

March 5, 2013 at 9:45 am
(10) olive roberts says:

Thanks alot for this idea.I may use this for science class.

September 24, 2013 at 5:07 pm
(11) Rodanne says:

This is so great thanks for helping me with my project

January 10, 2014 at 12:17 pm
(12) franny says:

this is my project

January 12, 2014 at 4:07 pm
(13) bgxjhfkgb says:

can someone give me information on it

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