Seasons and sky
Growing Degree Day
Direct answer
Growing Degree Day: A Growing Degree Day is a heat-accumulation unit calculated from daily temperature relative to a chosen biological base threshold.
Growing Degree Days accumulate temperature above a crop or organism base.
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At a glance
- Found in
- Seasons & Earth Almanac
- Related
- Slack Water, Heating Degree Day, Astronomical Season, Equinox
Growing Degree Days accumulate temperature above a crop or organism base.
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The story behind Growing Degree Day
Agricultural meteorology developed degree-day methods to connect weather records with recurring growth stages.
Why Growing Degree Day matters
They often track plant and insect development better than calendar date alone.
Growing Degree Day in practice: an example
Corn models often cap daily temperatures and accumulate units above a specified base rather than using raw monthly averages.
Where readings of Growing Degree Day go wrong
It is a mistake to transfer thresholds among species or regions, and do not treat degree days as a substitute for moisture, soil, or field observations.
Sources and editorial method
Research references used for this entry include:
- NOAA NCEI: U.S. Climate Normals - Official methodology and data for climate normals, degree days, growing seasons, and freeze dates.
- Source
- The Great Almanac Dictionary
- Category
- Seasons & Earth Almanac
- Last updated
- 2026-09-26
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Common questions
What is a Growing Degree Day?
A Growing Degree Day is a heat-accumulation unit calculated from daily temperature relative to a chosen biological base threshold.
What do people get wrong about a Growing Degree Day?
It is a mistake to transfer thresholds among species or regions, and do not treat degree days as a substitute for moisture, soil, or field observations.
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