So, I have data for streamflow volumes each month for ~75 years ... each year, the "max" streamflow occurs in some month (which varies). I want to know the percent of times it occurs in each of the 12 months over this 75 year timespan. What is the simplest way to generate that?

I have attached a screenshot of how the data is arranged in three columns (month, year, volume) ...

Any ideas? I would be so grateful!

Excel SS.png