Isoline map

Isoline maps are maps that use continuous lines to join points of the same value, i.e. equal altitudes (contour lines); equal temperatures (isotherms), etc...

The above Isoline map uses isothermic lines to divide up the continent of Australia into areas of equal tempatures during a typical month of January. So the two areas encompassed by cirlces/lines indicating 95 degrees means that entire area averages 95 degrees during the month of January.
http://mapmaker.rutgers.edu/355/interpolating-70-deg-contou.gif