How much water lands on Chicago from a one-inch storm?
Bill Porson, Chicago
A one-inch rainstorm delivers an immense amount of water. Chicago’s area is 228.5 square miles and Cook County is 946 square miles. 17,371,520 gallons of water are needed to cover one square mile to a depth of one inch; one gallon of water weighs 8.33 pounds. That means Chicago’s 228.5 square miles receive 3.97 billion gallons of water in a one inch rainfall, weighing just over 33 billion pounds. For Cook County, the comparable values are 16.4 billion gallons weighing 137 billion pounds. One inch of rain across Chicago is equivalent to 3,969,392,320 gallons of water whose weight is 33,065,038,026 pounds. Two inches of rain add 66,130,076,052 pounds!