USA NPN National Phenology Network

Taking the Pulse of Our Planet

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Winterkilled winter wheat

Freezing temperatures can severely injure winter wheat once it moves out of a vegetative phase and into a growth phase in the springtime.

Image credit:
R.L. Croissant,

Winter Wheat Development Forecast

Winter wheat is vulnerable to freezing temperatures once it resumes growth in the springtime.

Winter wheat current day forecast

Winter Wheat Current Day Forecast.

Winter wheat six day forecast

Winter Wheat 6-Day Forecast.

The USA-NPN winter wheat development Pheno Forecast indicates the approximate developmental stage of winter wheat plants based on daylength and recent temperature conditions. These maps are updated daily and available 6 days in the future.

Winter wheat is typically planted in the autumn. The plants germinate in late fall, overwinter as young plants, and resume growth in early spring. Winter wheat is cold tolerant in the overwintering vegetative phase but becomes sensitive to freezing temperatures once growth resumes in the spring (Shroyer et al. 1995). Plants are most sensitive to cold during reproductive growth, in booting and heading stages. At these stages, temperatures just below freezing can severely injure plants and greatly reduce grain yields.

The USA-NPN winter wheat development forecast can indicate whether plants at a particular location are likely to suffer damage due to sub-freezing temperatures.

Winter wheat developmental forecast

The USA-NPN winter wheat development forecast is based on the CERES-wheat model (Ritchie 1991), which predicts developmental stage using temperature, sun angle, and varietal inputs. The USA-NPN winter wheat development forecast assumes emergence has happened in the fall, and begins heat accumulation on January 1st to predict spring crop development. The forecast approximates across varieties to provide a general forecast for winter wheat development, which may reflect developmental stage in some varieties more closely than others. Developmental stages are estimated using accumulated growing degree days using the simple averaging method (base 32F, upper threshold 78.8F). We assume that plants have accumulated 1265 growing degree days (GDD) prior to winter and start GDD accumulation from this point on Jan 1. Further details

Developmental stage

GDD accumulation

Tillering, stem elongation










Seed development, maturity


These forecasts have been created with support from the USDA Climate Hubs and the Office of the Chief Economist.

More information on map development and re-use policy.

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