This map was produced by Mark P. Widrlechner, USDA-ARS, North Central Regional Plant Introduction Station, Ames, Iowa as an adaptation of climatic data published in:
Prikhot'ko, G.F. (ed.) 1968. Klimaticheskii Atlas Ukrainskoi SSR.
Gidrometeorologicheskoe Izdatel'stvo, Leningrad.
Graphic design by Rex Heer, Iowa State University.