Build a weather vane

A change in wind direction often indicates an imminent change in the weather. Be prepared for sudden change by making this weather vane. Then sit smugly under your umbrella as everyone else races off the beach in the downpour.

You will need:

a long pin e.g. a map pin
scissors
ruler
glue stick
thin, coloured card
drinking straw
2 pencils with eraser
compass

What to do:

Make a sandcastle. Alternatively if you’re not on the beach you will need to anchor an upturned yoghurt pot firmly.
Make a hole in the centre by inserting the pencil, sharp end first. Make sure that it is firmly in place.
With another pencil and a ruler, draw two large triangles and four small ones on the coloured card. Then cut out the shapes.
Place the small triangles on the base (of the sandcastle or yoghurt pot) as if they were the points of a compass. You may need to weigh them down (pebbles are very handy if you’re at the beach) or stick them to the bottom of the yoghurt pot.
Cut short slits in each end of the straw and insert one large triangle in each end to make an arrow-shaped "vane." Both points of the triangles should be pointing in the same direction.

Push the pin through the centre of the straw and into the eraser on the pencil sticking out of the sandcastle or pot. Make sure the vane swings round easily.
Watch the vane swing in the wind.
Finally, use your compass to determine East, West, North and South, and then label the small triangles accordingly. Now you can tell which direction the weather vane is pointing.
Sit with your back to the wind before eating your picnic!

What's going on?

Weather vanes are one of the oldest of all weather instruments; working by swinging around in the wind to show which direction it is blowing from. Traditionally, weather vanes had a religious importance and appeared in the form of weathercocks on church roofs as early as the 9th Century AD. The head of the cockerel would point into the wind, indicating the direction the wind was blowing from.

The direction in which the vane points indicates the direction from which the wind is blowing. For instance, in a westerly wind, the vane points "West."

The air is nearly always in motion, and this is felt as wind. Two factors are necessary to specify wind, its speed and direction. The direction of wind is expressed as the point of the compass from where the wind is blowing. Air moving from the north-east to the south-west is called a north-east wind. It may also be expressed in degrees from true north. A north-east wind would be 45°. A south-west wind would be 235°.

For more interesting facts about the wind
http://www.weatherwizkids.com/wind1.htm and
http://www.rcn27.dial.pipex.com/cloudsrus/wind.html

For more details of how to measure the wind
http://www.rcn27.dial.pipex.com/cloudsrus/measurewind.html

And if that has whetted your appetite for the weather then checkout
http://www.weather-climate.org.uk/05.php