To do this, have students fill a measuring cup with snow. I used a one-liter container marked in milliliters and filled it to the top, 1000 mL. In metric, 1 mL takes up 1 cubic centimeter of volume. So this amount of snow is also 1000 cubic centimeters.
Let the snow melt. Then divide the measurement of water by the original measurement of snow.
As an extension of this activity, you might ask students to calculate the weight of a specific depth of the snow that was tested, over an area such as the roof of a house. This is easiest with metric measurements because 1 cubic centimeter of water weighs 1 gram.