Weather: The Farmer's Variable
Despite advances in seed genetics, soil management, and pest control, weather remains the single largest determinant of crop yield. A well-timed rain during grain filling can add tonnes per hectare; a heatwave during flowering can devastate an entire harvest. Understanding the quantitative relationship between weather variables and yield is the foundation of agricultural forecasting.
Growing Degree Days: Nature's Clock
Plants do not respond to calendar dates — they respond to accumulated heat. Growing degree days (GDD) measure the thermal time a crop has experienced above its base temperature. Wheat needs roughly 1,400 GDD to reach maturity (base 10°C), while corn requires about 2,500 GDD. This explains why the same variety matures faster in warm climates and slower in cool ones.
Water and Heat Stress
Crop yield responds non-linearly to both water and temperature. Moderate water deficit activates stress responses that reduce but do not eliminate yield. Severe deficit during critical stages — flowering and grain filling — causes irreversible damage. Similarly, brief heat spikes above 35°C can sterilize pollen, causing empty grain heads even if the rest of the season is perfect.
From Weather to Harvest
This simulation generates a synthetic growing season using the temperature and rainfall parameters, then calculates yield from accumulated GDD, water availability, and heat stress penalties. Adjust the parameters to explore how climate variability translates to harvest variability — and why a few extreme days can matter more than seasonal averages.