Calendar days don't tell you how your crops are developing — heat does. This short explainer covers how GDD works for soybeans and why it's a more accurate measure of crop progress than days since planting.
Is 2026 a hot year or a cool year for crops? These charts compare how heat has built up so far this season against the same point in past years. The colored line is 2026 — if it sits above the dashed blue average line, the season is running warmer than normal and crops are developing faster than usual. The shaded band shows the full range from the coolest to the hottest year on record (2015–2025).
The amber dashed lines show key crop stage thresholds for your selected hybrid or maturity group. Where the 2026 line crosses a stage threshold is roughly when that stage was reached this season.
How GDD is calculated: Each day, add the high and low temperature together and divide by two to get the average. Subtract the base temperature of 50°F — and that's the day's GDD. For example: high of 85°F, low of 55°F → average of 70°F → minus 50°F base → 20 GDD. Those daily totals add up from January 1st through the end of the season.
What it means for your operation: A season running well ahead of the average means earlier crop maturity — which could mean an earlier harvest window and earlier pest pressure. A season running behind means later maturity and increased risk of a frost cutting the season short before crops finish.
Not all dry periods hit crops equally — the growth stage determines how much yield is at risk. For corn, the window from tassel through blister (R2) is the most sensitive: a single week without rain during pollination can cut yield 3–8% per day of stress. After dough (R3), corn has mostly set its kernel count and tolerates dry weather better. For soybeans, pod set through seed fill (R3–R5) is the critical window — drought during pod set reduces pod count, and drought during seed fill shrinks the beans already in the pod.
Enter your planting dates on the GDD & Crops tab to see your current crop stage. The stress alert above will update based on where your crops are in their development.
Rainfall chart: Shows how much rain has accumulated since January 1. A 2026 line running below the average means it's been a drier than normal year — your soil started the season with less moisture to draw on. A line above average means good moisture going into the growing season.
Crop water demand chart: Shows how much moisture heat and sun have pulled from fields since January 1. A 2026 line above average means it's been a hotter, sunnier year — crops are burning through soil moisture faster than normal. When rainfall is below average AND crop water demand is above average at the same time, that's when drought stress compounds quickly.
| Year | Last Spring Frost | First Fall Frost | Season Length | Total Rain" | Corn GDD | Soy GDD (est.) |
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