Isohyets

http://www.nzdl.org/gsdlmod?e=d-00000-00---off-0ccgi--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0-0-11-1-0utfZz-8-00&cl=CL3.6&d=HASHda30a7db653254f3b1261d.7&gt=2

A Isohyet map shows lines connecting points having the same amount of rainfall in a given period. Weather forecasters probability use these lines the most. I think they are a good indicator of how much rainfall an area gets.