Isohyet

1. 

http://www.dpi.nsw.gov.au/agriculture/field/pastures-and-rangelands/establishment/clover/part-f---choosing-the-right-sub-clover-v

An Isohyet is a line drawn on a weather map to indicate which areas received an equal amount of rainfall during a set time period. The line itself connects two points and segments that area as shown in this map.