coords.zone

Hardiness zones outside the US: what Australia, the UK, Sweden, and Germany use instead

The USDA scale is American, but several countries publish their own hardiness systems that do not map onto it one-for-one. Australia uses a 7-band ANBG scale, the United Kingdom a 9-tier H1a–H7 rating, Sweden and Norway a 1–8 scale that runs backwards from USDA (higher means colder), and Germany a Z-prefixed relabel of the USDA bands. Everywhere else, USDA 1a–13b is the usual fallback. The /api/v1/zone endpoint returns both the USDA zone and the local one for any coordinate, and no API key is required to try it.

One call, both scales

Latitude 59.33, longitude 18.06 — central Stockholm: 

curl "https://coords.zone/api/v1/zone?lat=59.33&lng=18.06"
{
  "lat": 59.33,
  "lng": 18.06,
  "usda_zone": "7b",
  "local_zone": "3"
}

local_zone is null for coordinates in countries with no separate system — including the United States, where the USDA scale already is the local one.

Verified examples

Every row below is a live response from the endpoint:

Location lat, lng usda_zone local_zone
Sydney, Australia −33.87, 151.21 11a 5
London, United Kingdom 51.51, −0.13 9a H3
Stockholm, Sweden 59.33, 18.06 7b 3
Munich, Germany 48.14, 11.58 7b Z7b
Cape Town, South Africa −33.92, 18.42 11a 2
Boston, United States 42.36, −71.06 6b null

Reading a local_zone value

Each scale has its own range, direction, and notation. What you need to know to render or compare a value:

Australia — 1 to 7

Seven bands rather than the USDA's twenty-six, and higher still means warmer. Sydney returns 5.

United Kingdom — H1a to H7, 9 tiers

Nine tiers written with an H prefix, so the value is a string, not a number. H7 is the hardiest end and H1a the most tender; the H1 band is subdivided into H1a, H1b, and H1c, which is why sorting these alphabetically will not give you the right order. London returns H3.

Sweden and Norway — 1 to 8, inverted

The one most likely to trip up an integration: 1 is the mildest and 8 the harshest, the opposite direction from USDA. A Swedish zone 3 is not "colder than zone 7" — it is considerably milder. Do not carry a comparison written against USDA numbers over to these values unchanged.

Germany — Z1a to Z13b

The German zones are a renumbering of the USDA bands with a Z prefix, so the two line up exactly: Z7b means what USDA 7b means. Munich returns 7b and Z7b together.

South Africa — 1 to 5

Five bands, higher meaning warmer. Winter cold alone describes South African growing conditions poorly — the country's summer- and winter-rainfall regions differ sharply in what they will support — so a South African zone and a USDA zone answer different questions. Cape Town returns 2.

Listing a country's zones

To populate a dropdown, /api/v1/country returns the full set of zone values in use at that coordinate's country: 

curl "https://coords.zone/api/v1/country?lat=51.51&lng=-0.13"
{
  "lat": 51.51,
  "lng": -0.13,
  "name": "United Kingdom",
  "iso_code": "GB",
  "zones": ["H7", "H6", "H5", "H4", "H3", "H2", "H1c", "H1b", "H1a"]
}

For a country with no local system, zones contains the full USDA list, 1a through 13b — so the field is always safe to render without special-casing.

Accuracy and provenance

Every zone is computed from ERA5-Land, the highest-resolution reanalysis in ECMWF's ERA5 family, over decades of record. Coverage is therefore consistent worldwide rather than stitched together from national maps of differing vintage and quality — the same call works for any land coordinate on Earth.

The local zones are approximations of each country's published system, not licensed reproductions of its official maps. Germany's aligns exactly, since its bands are a relabel of USDA's own. The Scandinavian one is the loosest fit, because the official Swedish map was hand-surveyed and folds in local factors that no global climate grid resolves. Use these for programmatic filtering and defaults; do not present them as a country's authoritative published zone.

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