AgriAuditor climate planning tool
Growing degree day and frost window calculator
Does a location usually provide enough heat units and frost-free time for a crop or maturity class? Compare the answer against a dated historical weather period, visible assumptions, and an uncertainty range.
What this tool answers
It estimates accumulated GDD after a selected planting date and summarizes last spring frost, first autumn frost, and frost-free days as historical percentile ranges. The selected coordinates and weather period are part of the answer, not hidden context.
Heat units
Daily temperature mean minus base temperature, with an optional maximum-temperature cap.
Frost risk
10th, median, and 90th percentile dates rather than one guaranteed frost date.
Coverage
The source, period, missing days, and fallback status are returned with every result.
Run the historical comparison
The result uses the exact coordinates, dates, and temperature assumptions you submit. It will not replace a missing weather record with a hidden preset.
Method and sources
The default primary weather request uses Open-Meteo's historical API with the ERA5-Land model. ERA5-Land is a Copernicus Climate Change Service reanalysis product. If the primary request fails, the API identifies the documented fallback instead of silently substituting a preset.
For context on degree-day terminology, see NOAA's GDD explanation and the Copernicus ERA5-Land dataset record.
AgriAuditor crop-profile base temperatures and GDD requirements are references, not cultivar guarantees. When you enter your own threshold, the result labels it as a user assumption.
Refresh owner: AgriAuditor data-pipeline maintainer. Recheck the weather endpoint, source record, and crop assumptions when the upstream product or calculation method changes. Qualified agronomic review is still required before treating this page as validated decision guidance.
Use the result in a wider decision
A climate window is one screening check. Continue with a coordinate-level field audit for mapped soil, climate context, crop fit and modelled economics. Use the crop ROI estimator only after replacing benchmark assumptions with local records.
Do not interpret this page as a guarantee of emergence, maturity, yield, profitability or crop success. Field elevation, slope, water, soil temperature, cultivar maturity and management still matter.
Read the AgriAuditor methodology →Questions about GDD and frost windows
What are growing degree days?
Growing degree days are a heat-accumulation measure. This calculator uses the daily maximum and minimum temperature mean, subtracts the selected base temperature, and floors negative values at zero.
How does the upper temperature cutoff work?
When supplied, the cutoff caps the daily maximum temperature before the daily mean is calculated. It is an editable assumption because crop and extension methods differ.
How are the frost dates calculated?
For each historical season, the calculator finds the last minimum temperature at or below 0°C in the first half of the local year and the first such minimum in the second half. It reports 10th, median, and 90th percentile dates across the seasons with complete observations.
Does the result tell me the exact planting date?
No. The dates describe historical weather patterns at the selected coordinate. Soil temperature, field microclimate, cultivar, soil moisture, pests, and farm operations can change the decision.
Why does the calculator ask for a historical period?
A multi-year period shows the spread of seasonal heat and frost timing instead of presenting one year as normal. Missing temperature days are counted and disclosed in the result.
Can I use a Fahrenheit base temperature?
Yes. The form accepts Celsius or Fahrenheit for user-entered base and upper temperatures, then converts them to Celsius before applying the calculation.