Degree day index for regional climate classification

Date or time period: 1940s

Amerine & Winkler[1] developed a heat summation index (based on de Candolle) for viticulture in California: confined heat summation base 50°F to the period 1 April to 31 October corresponding to growing season. California growing areas were assigned to five climatic regions on this basis


  1. Amerine, M.A. and Winkler, A.T. (1944). Composition and quality of musts and wines of California grapes. Hilgardia (University of California) 15: 493–673.