Isopleth: Isotherm (temperature) Map

http://www.middleschoolscience.com/isotherms.htm

Isopleths are contour lines that depict a certain variable which cannot be measured at a specific point. They must be calculated from data that is collected over an area. Examples of these are Isobars (air pressure), Isotachs (thickness), and Isohyets (rainfall). They are displayed using contour lines where connecting points of the line have the same "amount" of measured data. Above is an example of an Isotherm (temperature) map of the US during a specific period. It also uses shading to differentiate between different areas of temperature change.