Data & methodology
How when.garden knows when to plant
Every figure is precomputed from public climate data, then labeled with its source and a confidence score. We never present a modeled grid estimate as a local station reading.
The method, briefly
- Derive last/first frost probabilities and frost-free days from the nearest dense station history (NOAA GHCN-Daily), else model them from the NASA POWER grid.
- Classify each location's Köppen zone. Frost zones plant relative to frost dates; tropical zones plant relative to wet/dry seasons from POWER precipitation.
- Anchor each crop's sow / transplant / harvest windows to those dates using a curated offset table, then attach a confidence derived from data source and season fit.
Sources & licenses
NOAA GHCN-Daily
Public domain (CC0)
Daily station observations — the basis for last/first-frost probabilities (50% & 10%), frost-free days and growing degree days where stations are dense.
NASA POWER Agroclimatology
US-gov open, 0.5° grid
Fills gaps in sparse regions. Anything derived from it is tagged source = modeled and shown with lower confidence.
FAO ECOCROP
FAO open data
Crop temperature, precipitation and photoperiod ranges — the breadth behind our crop list.
Köppen-Geiger 1km (Beck et al. 2023)
CC BY 4.0
Climate-zone classification and the frost ⇄ tropical regime switch.
OpenStreetMap / Nominatim
ODbL
Place names and coordinates.
Building an app on this data? See the developer API.
Provenance & reproducibility
Every published figure resolves to the source snapshot, the parameters, and the pipeline stage that produced it. Frost dates are derived over the WMO reference window with a minimum station history before we publish them.
- Reference window: 1991-2020
- Minimum years: 20
- Frost threshold: 0°C
- Gap-fill: >50 km or >300 m → modeled
- Method: curated
- FAO ECOCROP — FAO open data
- NOAA GHCN-Daily — Public domain (CC0)
- Köppen-Geiger 1km (Beck et al. 2023) — CC BY 4.0
- NASA POWER Agroclimatology — US-gov open data
- OpenStreetMap / Nominatim — ODbL