Isohyets

http://www.sciencedirect.com/science/article/pii/S0169555X06003588

Isohyets are maps that measure rainfall. The contours lines used in the map intersect other lines with similar representing the exact value of precipitation. Shading is also used to convey how much precipitation an area receives with the legend at the bottom. The map above shows exactly that and shows how much precipitation the individual islands that comprise Hawaii receive as well as the Kohala Peninsula which the map focuses on.