Isohyets

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

Isohyets are line that connect areas of equal rainfall amounts. These values can change over different seasons and also over longer periods. This example shows the isohyets in Southwestern Australia. With isohyets, it is easy to observe how rainfall amounts increase as we move toward the coast.