It doesn’t actually matter how wide container is, so long as it’s the same diameter all the way through. As the volume of the container gets bigger—from say, a coke can to a mop bucket—so does the area which collects the rain. Because of this, one inch of rainfall will be recorded consistently between cylinders of varying sizes. [2] X Research source
Rocks, stones, marbles: any small, relatively heavy objects will do, as long as it won’t absorb any of the water. If you’ve created your own gauge with a soda bottle, make sure the entire bottom (the four separated points of the base) is filled with water and stones, to provide a flat starting point for your scale. As an alternative to placing pebbles in your gauge, you could place it within a sturdy container, such as a heavy bucket or flowerpot.
If you’ve opted to go pebble-free and are going to place your rain gauge inside a flower pot, you won’t have any water in your gauge yet. In this case, zero will be at the bottom of your container.
It’s important to check it every day even if there hasn’t been any rain. You can lose water from evaporation, and water mysteriously showing up in your rain gauge without the accompanying rain clouds might mean your rain gauge needs a new spot (sprinklers are a common culprit).
The formula for finding an average is easy to apply. The average equals the sum of all the items (in this case, rainfall measurements for a day, week, or month) divided by the number of items (however many days, weeks, or months you’ve added up). [6] X Research source If you’re looking for average weekly rainfall over 4 weeks, with recorded weekly rainfall totals of 20 inches, 12 inches, 6 inches, and 25 inches, we would say 20 + 12 + 6 + 25 = 63 (the sum of the items) / by 4 (the number of weeks) = 15. 75 inches average weekly rainfall.
