Growing degree days and heating degree days used to confuse me too! I figured they should go in the same direction, but they don't! This is because heating degree days are a measure of how much you have to heat your house to keep it at a reasonable temperature - this value gets HIGHER the COLDER it is outside. On the other hand, growing degree days are a measure of how quickly an organism can develop, based on the external temperature, and this value gets higher the WARMER it is outside.
Gee, I hope I'm right about this!! It came to me in an epiphany once while I was listening to the ag report.
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Bernadette Roche
Department of Biology
Loyola College
4501 N. Charles St.
Baltimore, MD 21210
broche at loyola.edu
410-617-5591
