GDD Calculator Guide

The Growing Degree Day (GDD) Calculator tracks heat accumulation to predict vine development stages.


How to use it:

  • Enter daily high and low temperatures
  • Select your base temperature (default: 50F for grapes)
  • Add multiple days to track cumulative GDD

    • Key GDD thresholds (base 50F):

  • 100-200: Budbreak
  • 500-700: Bloom (critical spray window)
  • 1400-1600: Veraison
  • 2000-2800: Harvest ripeness

    • Data sources: Use your on-site weather station for best accuracy. CIMIS (California), local ag extension, or nearby airport stations can supplement.

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