Snow is 1/8 as heavy as water.
That means 1 cu. Inch of rainfall results in 1/8 cu. Inch of snow
So, 3.5 cu. Inch of rainfall results in [ 1/8* 3.5] cu. Inch of snow
0.4375 cu. Inch of snow
Therefore 0.4375 cu. Inches of snow would weigh as much as 3.5 cu. inches of rainfall.