MAKE IT RAIN 

MATERIALS:

• glass mayonnaise or canning jar (something with a metal lid)
• hot water
• hammer and a nail
• ice cubes
• salt

PROCESS:

Take the hammer and make some dimples (about 5 or so) into the lid. Make sure they don't puncture the lid, indentations are what we're after here.

Next, boil some water and then place it into the jar. Take the lid and place it, dimples and all, upside down ontop of the jar. Make sure you have made your dimples so that when you place the lid down in this fashion the dimples are undulating downward.

After about a minute or two with the lid overtop of the boiling water in the jar, add a few ice cubes into the lid. Add some cold water and salt, and stir it up. Make sure the jar itself is always completely covered by the lid and no steam gets out.

Within a few minutes, drops of water (rain) should materialize and drop from the dimples down into the water below.

EXPLANATION:

What happens? Much like the way a cloud forms, warm moist air converges with the colder air above it. Saturation of the air is achieved pretty easily in the covered jar (much more easily than an uncontrolled atmosphere). The salt adds a 'condensation nuclei' to the water, making it easier for water droplets to form (much like what goes on in our atmosphere-- nearly every raindrop has some sort of salt particle or other element at its nucleus.