What is the average amount of rain...

We couldn’t find a way to calculate this for the entire Earth. We did find that the continental United States receives enough precipitation in an average year (calculated at 31,536,000 seconds) to cover the land area to a depth of 30 inches. That works out to about 1,430 cubic miles of water and a weight (at about 62.4 pounds per cubic foot) of about 6.6 billion tons — an average of more than 2 tons of rain per second.