While you can collect rain in any container marked off in inches (or centimeters), you can actually make a gauge that is more precise. The best container for collecting rain is a wide-mouthed one. If you can find a wide funnel that will fit inside it, all the better, because the funnel will keep some of the rainwater from evaporating before you get a chance to record its depth. But measuring a small amount of rain in such a large container is difficult. Thereâs a trick for making more precise measurements.
In addition to the container you have sitting outside collecting rain, you will need a tall jar that is only 1″ to 1 1/2″ in diameter (olives come in jars like these). Fill your collecting container with exactly one inch of water. Pour the water into the tall jar and mark the level of the water. Divide that inch (and any others you wish to mark on the jar) into fractions.
Whenever it rains, collect the rainwater in the bigger container, but transfer it to the measuring jar to see how much rain really fell.
[Image: Courtesy of Flickr user cityofsound]