MATERIALS:
• Can, at least 3 inches in diameter
• Water
• Masking tape
• Glass jar, about 1 1/2 inches in diameter
• Ruler showing inches and centimeters
• Permanent marker

STEP 1
Take the large-diameter can (for collecting the rain) and pour 1 inch of water into it. Measure as carefully as possible. Pour the water into your smaller diameter jar (for measuring the rain).

STEP 2
Place a strip of masking tape vertically on the outside of the jar, and mark both the level of the water and the bottom of the jar on the inside. Measure the distance between those two marks and divide by ten, then mark those increments off on the tape--this will give you an easy-to-read scale showing rainfall in tenths of an inch. (Use the centimeter side of your ruler for this step.)

STEP 3
Set the collecting can outside, away from the house, trees, or anything else that might interfere with a clear rainfall. After a storm, pour the contents of the collecting can into the measuring jar and note the results. Should you get more than one inch of rainfall at one time, pour the water off an inch at a time, until the can is empty. Don't forget to check the can soon after a storm, or some of your data will evaporate.