How can we account for snowfall in precipitation and I/I data?

Most I/I studies look to quantify rainfall entering a sewer system as I/I.  As a result, frozen precipitation events that occur during an I/I study are often ignored.  Keep in mind that the most intrusive effects of I/I on a sewer system result from rainfall, not snowfall.  Some municipalities in colder climates have an interest in this, but the analysis is not straight-forward and can be problematic.