One rain measuring method we studied in a Physical Geography
class I took once is called the tipping bucket gauge.  A rod is
connected to a shaft that can turn a counter and probably also
provides some detent to position it correctly.  The rod is normally
vertical with a small bucket on each end.  At any given time, one
bucket is pointed toward the sky to catch water and the other one is
upside down and empty.  When the top bucket fills, the weight flips
the rod which increments the counter, spills the full bucket and
brings the other bucket up so it can fill.  The process continues and
the counter counts the number of buckets filled.  Such an arrangement
could be easily adapted to use a PIC as the counter.

        We studied this briefly in class and the instructor said it was
used in areas that get lots of mist.  I am not sure how well it would
work in high wind.

Martin McCormick